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Патент USA US2110910

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March 15, 1938.
Filed Aug. 23, 1935
4 Sheets-Sheet l
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March 15, 1938.
Filed Aug. 23, 1935
4 Sheets-Sheet 2
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March 15, 1938.
Filed, Aug. 25, 1935
4 Sheets-Sheet 3
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March 15, 4-938.
Filed Aug. 25, 1935
4 Sheets-Sheet 4
?zz/wen Amman/r 5464015,?
6%; Xian/4K0 (an-519s
Patented Mar. 15, 1938
and Charles Leonard
Bernard‘ Anthony Hensler
Peters, London, England, assignors to Sie
mens Brothers & Company Limited, London,
Application August 23, 1935, Serial No. 37,484
In Great Britain August 29, 1934
(C1. 179-—27)
'7 Claims.
This invention relates to telephone systems and
more particularly to an arrangement suitable for
use in a toll or trunk telephone system wherein
each incoming call causes a switching apparatus
5 to set itself to a position indicative of the order
of arrival of the call with respect to other calls,
the several switching apparatus so set being re
leased in the order of arrival of the respective
calls and are thereupon caused to search for a
10 free subsequent circuit as these are rendered
available. The setting and release of the switch
ing apparatus may ‘be controlled by a chain of
relays which are operated and released respec
tively to control such operations, and the system
15 may be applied to a toll or trunk system wherein
calls are set up on demand by operators, i. e. a
“demand system”.
A system of this type has already been sug
gested in which a distributor switch on being set
20 in motion by an incoming call searches for and
tests into an outlet to a display panel and if
other calls are awaiting’ attention the call vis
added to a queue,vthe switches stepping on and
so moving the call to the head of the queue as
earlier display positions become available.
there are no other calls waiting in a queue and a
subsequent circuit is available the distributing
switch nevertheless tests into the ?rst display
position and is immediately released to search
30 for the subsequent circuit.
In the present invention improved call queueing
arrangements are provided by arranging that in
moving ,a call up the queue the distributing
switches do not step but a common switching
35 mechanism associated with the display effects
the moving up process .byyproviding for the re
lease of the switches in the display positions in
ing to the order of thecall with respect to other
calls which have failed to be connected to sub
sequent circuits. The several switching apparatus
are released from such positions in the order of
.arrival of the calls as subsequent circuits are 5
rendered available to search for these circuits.
According to another feature of the invention
switching apparatus taken into use by‘ incoming
calls and formed into a queue remains in the same
position during the movement of the call to the 10
head of the queue until it is released to search
for a subsequent circuit for the extension of the
The arrangements on which the incoming calls
are thus “queued” may consist of a number of
relays which are operated seriatim as the calls
take a position in the “queue”, and arrangements
maybe provided whereby the relays are picked up
in a continuous order of rotation irrespective of
the actual relative position of a call in a queue.
In the application of the invention to a nor
mal or semi-automatic system arrangements are
provided for giving relief to the demand oper
ators, by signalling a further operator or oper
ators when more than a certain number of calls 25
are “queued” up. The furtheroperator or oper
ators may normally deal with other types of in
coming calls.
In order toeffect a certain economy modi?ca
tions to- the system of the prior invention may be 30
made whereby incoming lines are connectable to
the switching apparatus already referred to over
a searching switch, the switching apparatus hav
ing full availability ,to the subsequent connecting
One method of carrying out the invention is
This arrangement is especially advantageous
described by Way of example in the following
description of the. arrangements illustrated in
the accompanying drawings, wherein the inven—
40 where the distributing switches are high speed
telephone system in which under normal traf?c
turn as subsequent ‘circuits become available.
motor driven switches as the step by step action
in the queue is avoided. A furtheradvantage is
gained by placing the display positions at the
end of the distributing switch bank so that if
a subsequent circuit is available at a time when
there are no calls in the queue a searching dis
tributing switch is not stopped momentarily in
a display position but proceeds directly to the
outlet to the subsequent circuit.
It is, accordingly one feature of the present
invention that switching apparatus taken into
use by an incoming call is caused to‘ search for
a free subsequent circuit, such as a connecting
circuit on an operator’s position and if this search
is unsuccessful to assume a position correspond
tion is illustrated as applied to‘ a toll or trunk 40
conditions calls are dealt with in the demand
basis. It is to be understood that the invention
is not con?ned on its application to such systems,
but is capable of utilization in any system of call 45
In Fig. l of the drawings are illustrated an in
coming line circuit ILC, and a call distributor
circuit DD. There is also illustrated a portion
of .an operator's cordless. connecting circuit CC, 50
of which there is provided a number on each po
sition, and a portion of an operator’s position
circuitOPC, only those circuit elements of these
latter circuits necessary to the understanding
of the present invention being shown.
In Fig. 2 is illustrated a lamp display circuit
LDC, calling lamps DOP on a demand position
and calling lamps OOP “demand” and “incom
scribed in detail hereinafter.
ing” on a further or omnibus position.
by step switches or uniselectors AB and BA. The
A fur
The lamp display circuit Fig. 2 includes step
ther portion of an operator’s position circuit OPC
is shown in this figure.
only the arc ha! of switch BA is shown, the other
An incoming line circuit ICL Fig. 1 includes
a step by step switch or uniselector P having
arcs of the switch BA being associated with the
lamp multiple extending over the arcs ab6—ab8
wipers and arcs pl to p5, driving magnet PDM,
The line relay is
and the method of connection of the multiple t0
10 and interrupter contacts pdm.
designated LA, the test relay TA and a switch
ing relay H. The incoming line, junction or
trunk is designated JCT. The arcs p2 and 103
are concerned with the connection of the speak
tions of the relays CG, CN, and MN will be de
ing wires, the arc pl with the testing circuit,
the arc M for determining the type of call, i. e.
whether it is an ordinary call or one from a coin
box. The arc p5 is a homing arc.‘
The distributor circuit includes a motor driven
switch or uniselector D with wipers and arcs I,
la, . . . 4, 4a, and a latch magnet LM.
The cir
cuit for and the driving motor of the switch being
well known per se is not shown.
Each arc of contacts consists of two rows of
25 52 contacts each, a‘ double-ended wiper being
adapted to traverse the rows in succession. The
arcs are associated in pairs, namely, l and la,
2 and 2a, and so on, and it is arranged that dur
ing search when the wipers of an arc have trav
ersed the contacts in both rows of the are a
switching relay WS is operated to connect the
main circuit wire to the wiper of the other are
of the pair. The arcs I, and la, and 2, and 2a,
are for connecting through the positive and neg
ative wires, and the arcs 3, and 3a, and 4, and 4a,
are concerned with testing into the connecting
The connecting circuits at the several opera
tors’ positions are connected to the contacts on
40 the several arcs.
To the ?nal eleven contacts
in the second set of contacts of are 401. are con
nected the wires 1d, and OF which lead to the
lamp display circuit Fig. 2. Connections are
also made from certain of the ten contacts in
arcs 3a and 2a corresponding to the contacts of
arc to to which the wires ld are connected, the
purpose of these connections being explained
fully hereinafter. The connecting circuits are
over‘ the
of the distributor
switches of the several distributor circuits, the
connecting circuits including those on demand
positions, omnibus and other relief positions.
There is provided a line relay L, a releasing relay
B, a testing relay T, and switching relief relays
55 S and SS respectively. The relay TCO is pro
vided for determining the origin of a call, e. g.
whether it has been originated over an ordinary
line or a call box line. The relay RR is a ringing
relay for applying a ringing current back to a
calling party. The functions of relay D8 will
be best understood from the subsequent detailed
description, but generally they are to modify
the testing circuit for testing in to the connecting
circuits after a call has been released from asso
ciation with the lamp display circuit.
The portion of the connecting circuit illus
trated in Fig. 1 shows contacts SPKI, SPKZ and
SPKS of a speaking key and relays SK,.SL, BA,
and AS this being the order in which the relays
are operated. The functions of the relays Will
be best understood from the following detailed
description. The elements of the operator’s cir
cuit CPC Figs. 1 and 2 include contacts CA! and
CA2 of a call answering key, and contacts. RA
75 (Fig. l) of a release answering key. 'The func
arcs abl . . . abB of switch AB are shown, but
the arcs will be readily understood from the con 10
sideration of the wiring of arcs ab6-ab8. The
multiple wiring from the arcs ab6—ba8 extends
to the display lamps l—il on the demand opera
tors’ positions DOP, and it will be seen that the
multiple wires over the arcs are slipped at each
are so that the ?rst contact of the arc abB is
connected to the wire leading to display lamp
l, the ?rst contact in the arc ab‘! is connected
to the wire leading to display lamp 2 whilst the
multiple wire to lamp l appears at the second 20
contact in the arc and so on over the remaining
The “demand” lamps on the omnibus po
OOP are connected in parallel with the
on the demand position DOP.
are ab'l is concerned with the stepping and 25
homing of the switch AB, and the object of the
arcs c122 and ha! is to ensure that the switches
AB and BA are always in alignment, the relay
SY controlling the stepping of the switch BA
to bring it into alignment with switch AB.
The wires Zdl——ill from the arc 4a of the dis
tributor switch are connected seriatim to the
relays A—J, contacts of the relays A—J being
connected seriatim to the wipers of arcs ab6—
The functions of the various relays shown will
be best understood from the subsequent detailed
An omnibus position normally deals with in
coming calls signalled on the “incoming” lamps 40
quite independently of the traffic on the demand
operator’s position "unless excessive congestion
exists on the latter, whereupon the “incoming”
lamps on a particular omnibus position or posi
tions are disconnected and the “demand” lamps
connected up by the operation of relay AA. Such
a condition is indicated to a supervisory operator
over the lead SP.
The general operations of the arrangements il
lustrated are as follows: Upon a call being made
over a junction or line JCT the switch P in ILC
searches for and tests into a free distributor cir
cuit DD.
Normally one or more demand operators will
have a position connecting circuit assigned which
is brought about by throwing the speaking key
SPK associated with the connecting circuit and
the call answering key CA in the position circuit.
On the seizing of a distributor circuit DD the
switch D is caused to hunt for an assigned con
necting circuit, and when such is found the call
ing party is switched through to the operator who
then sets up the desired connection.
If the call had originated at a call box or over
a line demanding special treatment, the operator
would receive a tone on the origination and
switching through of the call, and then cause
the conversational connection to be set up by
throwing a key (not shown) in the connecting cir
cuit which applies earth to the negative wire.
The operator controls the release of the call
and can release it by throwing either the key REL
in the connecting circuit CC or the key RA in
the position circuit OPC.
In the event of a call being made whilst a. con 75
necting circuit is not assigned, the distributor
switch hunts until afreecircuit over one- of the
display leads Id is found and tests into this to
cause a calling lamp to light, and busies the cir
cuit against other searching distributor switches
which will test into the other displaycircuit
leads. The calls are thus ‘caused to be queued up
in the order of origination, and when the display
circuit is fu1l,‘i. e. ten calls arestored," other
searching distributor switches test into an over
?ow circuit over the lead OF to which" the call
meter CM is connected at this time to indicate
the number of calls so» held.
An operator causesthe release of the call from‘
15 the head of the queue by simply assigning a con
necting circuit, the distributor switch associated
with this call then being released ‘from the dis
play to search for the assigned connecting cir
cuit whereupon the switches AB and BA step
20 tomove up, in effect, the remaining calls in the
queue one in the order ‘of their priority of call
ing. Calls held on the over?ow circuit are re
leased and one of these tests into the lamp cir
cuit just freed which now is so connected as to
25 place the call at the lowest position in the queue,
whilst the other calls are again connected to the
over?ow circuit.
If a call is held in the display circuit for more
the wiper pl meets a free outlet relay TA op
erates from the battery ‘potential, over are pl,‘
and contacts ms‘; The driving circuit for the
magnet PDM isopened and an obvious circuit
is closed for the right-hand ‘coil of relay H at
contacts tal. Relay H operates and at contacts
hl locks itself temporarily over its left hand coil
to earth over contacts lal, and at contacts hZ
prepares a point in a locking and busying circuit
over which it locks on the release of relay LA.
At contacts 71.3 a furtherpoint in the driving
circuit for magnet PDMis opened. Contacts 116
prepare a circuit for the operation of relay TCO
over its coil (I) and arcs p5 and p4, but however
as the line calling is an ordinary line no con
nectionv is made to the contact in are 124.
At contacts M and- n5 relay LA is disconnected,
relay LA being slow to release and does not re
lease immediately and the incoming loop is ex
tended to relay L in DD over contacts rrl and 20
W2 and relay L operates. A circuit is closed for
relay B from earth over contacts 885 and ll and
relay B operates.
Contacts Z2 prepare a holding .
circuit for relays SS and DS, and, contacts 13
prepare a holding circuit over the arc pl for 25'
holding the circuit ILC. Contacts l4 prepare a
supervisory circuit for the supervision of the
Upon the operation of relay B an earth is ap
than a predetermined period a ‘timing circuit
over contacts M and are pl to short cir 30
30 ‘i‘comes into operation to cause calling. lamps to
cuit relay TA, hold relay H, and busy the outlet
light on a relief position (over the lead AL Fig.‘
at the preceding selector if such has been em
2) so that a relief operator is signalled. Similar
ployed. Relay LA releases shortly after relay B
ly, in the example described, a relief operator is
and-disconnects relay TA. Contacts 122
signalled if the number of calls in the queue ' operates
connect a ‘ringing signal tone from lead RS and
.areaches seven, the relief operator being held un
over contacts as? to the positive wire and thence
til the number falls below six; If the number to the calling party. Contacts b3 close a point
of calls in the queue reaches nine then the “in
in the circuit for the test relay T.
coming” lamps associated with a particular 10m
A circuit is closed from earth over contacts
nibus operator’s'position are disconnected, and the tl, sl, i006, b4, latch magnet LM to battery and
“demand” lamps are connected in parallel with
and the latch magnet operates closing con
the lamps on the demand operator’s position earth,
tacts whereby-the circuit of a driving motor is
so that the omnibus operator'can assist the de
closed, the motor in rotating driving the wipers
mand operator. The omnibus position is dis
the distributor switch in known manner.
connected when the number of calls in the queue of Under
normal operating conditions, i. e. when 45
falls below eight.
calls can be answered on demand, a connecting
The circuit arrangements illustrated will now a
circuit, a portion of which is shown in the
be described in detail.
Assuming that a call is made over an ordinary rectangle CC, will be assigned on one or more oper~
ators’ positions, the assignment of a connecting
line, i. e. a:line from an ordinary local subscrib
circuit necessitating the throwing of a speaking 50
er or over a local selector, then a loop'will be
50 applied tolthe positive and negative wires JCT key SPK associated with the connecting circuit
CC and the connect answer key CA in the oper
resulting in the operation of relay LA over con
ator’s circuit OPC‘. On the closing of the con
tacts ~h4 and n5. At contacts lal earth isuap
plied tothe P wire-to busy the line at preceding tacts SPKZ a circuit is closed from battery over
selectors, if the call has been made over a selec-r a resistance in the operator’s position circuit OPC, 55
the coils of relay SK in series over the contacts
tor, and at contacts Za3 the test relay TA is con
nected to the wiper of the test are p1. A circuit SPKZ, contacts sZl to earth and relay SK oper
is closed from earth over contacts tal, M, 1112, ates and at its contacts skl short circuits its left
pdm to magnet PDM to battery and magnet PDM hand coil. A circuit is closed from earth over
energizes and opens the contacts pdm whereby the left hand coil of relay MN in OPC, contacts‘ 60
bal, SPK3, s7c2, relay SL to battery and earth and ‘
the above circuit 'is broken and the magnet de
energized and the wipers of the switch are stepped relays MN and SL operate in series. Contacts .92!
hold relay SK over its‘ right hand coil independi
on to the first‘ outlet in their arcs.
ently of contacts SPKL ‘A battery potential is
If the outlet is busy the relevant contact in arc
applied to the contact in the are 4 or M of the dis 65 will be marked busy‘by an earth applied from tributor
D corresponding to the connecting cir
the distributor circuit DD and as a consequence
relay TA'will be short circuited and ‘prevented cuit, over relay BA, key contacts REL, contacts
from operating and therefore when‘ the contacts s13, 8M, key contacts RA and CAl in. OPC, and
pdm close 'on' the de-energization of themagnet contacts s12.
Assuming that an assigned connecting circuit
PDM the circuit for the magnet isxagain closed
and the wipers stepped on to‘the next outlet in exists in the arcs l, 2, 3, 4 of the distributor switch
D then the wipers of the switch are driven until
the manner before described.
A free outlet willv be marked ‘by a ‘battery po-. the wiper of are 4 meets the contact marked by’
battery over the relay BA, whereupon a circuit is
tent-ial overv contacts (m2, ssG and bl in the'dis
closed from earthscontact enl, (also shownin
2,110,910 ’
Fig. 2) contacts 120.3, arc and Wiper 3, contacts
wsd, s34, ds3, b3, recti?er 7', both coils of relay T
relay ASv in CC, the relay releasing ‘to light the
supervisory lamp ASL in front of the operator
in series, contacts ws5 to the marked contacts and
relay T operates and at contacts tl opens the
circuit for the latch magnet LM, whereby the
wipers of the switch D are brought to rest, short
at contacts cs2.
by operating the release key RA in OPC or REL
in CC and thereby release relay T which at con
circuits the upper coil of relay T, and relays T
and BA operate in series. The lower coil of relay
tacts ti short circuits relay S.
On the release of relays L and S the earth is
T is of low resistance and the earth over it busies
removed from the private Wire to the‘ circuit ILC,
and the preceding selector, and relay H is re 10
10 the outlet to the connecting circuit against other
searching distributors by preventing their T relays
from operating. At contacts ba2 relay BA locks
itself independently of contacts 812 and CAI, and
at contacts bal disconnects the left hand coil of
15 relay MN and connects in its place the right hand
coil of this relay in series with relay CG. Relays
SL and MN hold and relay CG operates. At
contacts 12113 a circuit is prepared for relay AS
but this relay cannot operate in series with the
upper coil of relay T owing to the disposition of
the recti?er 1'. Contacts had close the circuit of
the supervisory lamp ASL in front of the opera
When relay T operates and contacts tl change
25 over, a short circuit is removed from relay S, and
this relay operates in series with the latch magnet
LM, the latch magnet however not being energized
suiliciently in this series circuit to withdraw the
Relay S at contacts sl locks itself independ
ently of the latch magnet and at contacts s2 and
s3 prepares to extend the positive and negative
conductors to the connecting circuit CC. Con
tacts s4 prepare a point in a circuit for relay AS
in CC. Contacts 85 do not concern us at present.
A circuit is closed from earth over the 0115 nor
mal contacts onl, which as the switch is off nor
mal are closed, contacts s5, coil (I) of relay DS,
relay SS, resistance to battery and earth, and
relays SS and DS operate.
At contacts es! and over contacts Z2 a locking
circuit is closed for relays SS and DS independ
ently of the contacts onl and .95. Contacts ssZ
and $33 prepare further points in the positive and
negative wires to the connecting circuit CC.
Contacts 334 connect earth over Z4 and s4, and
over 10.94, ba3, relay AS to battery and relay AS
operates to disconnect and extinguish the super
visory lamp ASL at contacts 6052. A locking cir
cuit is closed for relay AS over contacts as! and
SPKl to prevent relay AS being released whilst
the speak key is operated. At contacts ss5 an
obvious circuit is closed for relay TCO and the
circuit for relay B is opened. Contacts $85 per
form no function at this stage. Relay TCO oper
When relay B releases after its slow releasing
period the circuit ILC, and the preceding selector
if such has been used, are held over contacts bl,
$86, and s6 and Z3 in parallel.
On the operation of relay TCO contacts i002
and i003 complete the connection of the positive
and negative wires to the connecting circuit. The
other contacts of relay TCO will be referred to
The operator may now converse with the call
ing party and completes the connection to the
wanted party. The speak key SPK in CC and
the key CA in OPC are restored and relays CG,
70 MN, and SL are released at SPK3. Relay SK is
released at contacts sZI, and relays BA and T are
held over the contacts ba2 and s13.
When the calling party clears the line, or
flashes the operator to call her attention, relay L
75 releases and at contacts 14 opens the circuit for
The operator may release the distributor circuit
leased which at contacts 716 closes an obvious
homing circuit for the switch P.
At contacts 35 the original circuit for relays SS
and DS(I) is opened, but these relays remain held
over onl, Z2, and ssl, and a homing circuit for the
switch D is closed over onl, 85, b4, LM to battery
and the switch commences to home and when the
home position is reached contacts on! open dis
connecting the circuits for the magnet LM and
relays SS and DS. Relays SS and DS release, 20
and relay SS releases relay TCO. The testing cir
cuit for the switch P is held open at contacts 0212
until the switch reaches home. The circuits are
now at normal in preparation for dealing with
further calls.
If the circuit ILC terminates a call box line the
connection from the arc M to the coil (I) of re
lay TCO over contacts tool! will be completed,
and it will be seen that on the operation of relay
SS relay TCO will be prevented from operating 30
over this coil as it is short circuited.
As a conse
quence: a tone will be given to the operator over
contacts i002 and the positive conductor and the
operator on observing such tone throws a key (not
shown) in the connecting circuit whereby an 35
earth is applied to the negative wire and relay
TCO is operated over its coil (II) and contacts
tcol3, ss3, and s3.
Relay TCO operates and performs the func
tions before described.
In the event of the assigned connecting cir
cuit being connected to the arcs la, 2a, 3a and 4a
of the switch D, then when the wipers meet the
last contacts in their arcs a circuit is completed
from earth last contact in arc 3, contacts ws4, ssll, 45
(183, 123, recti?er r, relay T, ws5, last contact in
arc 4, (coil (1) of relay WS to battery and relays
T and WS operate. At contacts wsl relay WS
locks itself over its coil (II) to contacts on]. At
contacts 1082-1085 the arcs I, 2, 3, and 4 are dis 50
connected and'arcs I 11, 2a, 3a, and 4a are connect
ed up. Contacts ws6 prepare to lock relay TCO
over its coil (I). The circuit of relayT is opened
when contacts ws5 change. over and relay T re
leases. Relay T is operated only for a very short 55
time which may be insu?icient to allow relay S to
Even so, if relay S does operate relay
SS and DS cannot operate as they are short cir
cuited at‘ this time by the connection of earth
over contacts 882, $2, ws2 and are I a, the earth to 60
the other side of the relays being derived over
contacts on! and .95.
The switch now searches over the second half
of its arcs for the assigned connecting circuit
and when this is found the operations as before 65
described take place.
If it is required to ring a calling subscriber who
has left the line the operator throws a ringing
key (not shown) in the connecting circuit where
by a battery potential is applied to the positive 70
wire which operates relay RR. At contacts rrl
and 7‘7‘2 ringing current over the leads R and
RRS is applied to the calling line.
In the event of a connecting circuit not being
assigned such as will happen at busy periods the 75
distributor switch D drives‘until the wiper of arc
' 4a meets the wires ld leading to the lamp display
circuit Fig. 2. Assuming‘ that the display is en
tirely free then when the wipe-rs of arc 4a. meets
the contact connected to the lead Zdl a circuit is
closed from earth over~contacts'tco1, arci3a,'con
tacts wsd, s34, (Z33, b3, recti?er 1*,relayT, contacts
It will-‘be seen that providing the‘ switches AB
and BA‘ are- standing in correspondingpositions
a circuit is closed over arcs ab2 :and bal for relay
SY which at contacts syl opens the self drive
circuit for the magnet BADM.
Upon an operator assigning a connecting cir
» cuit by throwing the speaking key SPK associ
ated with the connecting circuit and by throw
ws5, arc M, leadv Zdl, relay A (Fig. 2),‘arc a193, ring the connect answer key CA.v in the position
contacts col, st3, arc 11b4, resistance to battery ~ circuit OPC, a circuit is completed from earth,
Relay T on opera
contacts CA2, relay CN, contacts cgl, mnl,‘
tion allowsS- to'operate at contacts tl and locks over
(relay MN being operated at this time in series
itself in series with relay A independently of con
relay SL Fig. 1), e112, ac?, stl, lower coil
tacts tco'l. Relay SS and coil (I) of relay D‘Sare “with
of relay ST to battery and relay ST operates and
short circuited over contacts s32, 82, we! and are
locks itself over its upper coil and contacts st2,; L15
15 la. so that they cannot operate.
and ac5. When contacts stl are in the mid posi
A circuit is closed from earth over contacts ss3, tion
relay CN which is a very fast operating relay
s3; ws3, arc 2a, coil (II) of relay‘TCO to battery
vin series with the resistance and closes
.4 and relay 'I‘CO operates and looks over contacts
a circuit in series’with itself for-coil (II) of relay
'wsl and tool. At contacts i005 a circuit is closed CG over contacts c'nl but this coil is shunted for,
20 for relay DS over its coil (II) andicontacts ss5
the moment. Relay CG operates when contacts
and relay DS operates Relay B is‘held inde
pendently-of contacts ll. at contacts (152 so that stl change over and at contacts cgl‘ opens a
relay B cannot be released in the-event of the point in the operating circuit for the lower coil of
10 and relays T and A operate.
calling party leaving the line.
¢ ,
'When relay A, Fig. 2, operates it closes a locking
circuit for itself at contacts al independently of
" the arcs'ab3 and M24, and at contacts a2 prepares
a circuit for relay B. Contacts 413 prepare a point
in the circuit to'the overflowv lead‘ OF, ‘but this
relay ST;
A further point in the operating circuit for the; 25
lower coil of relay ST’ is opened at contacts stl
and this coil, beingjshunted, gives the relayslow
releasing characteristics.
~ '
Thus the signal transmitted from the operator’s
circuit OPC‘ to the relay ST is of very short dura-.:
ber of calls are‘storedlon the display. Contacts tion and occupies only‘ a part of the movement
a4 and all close in parallel and'completea cir v’ of the contacts stl, this minimizing the chances
of the simultaneous connection of two» operators’
cuit over arc abt for the calling lamp I on the de
30 circuit is not completed until a» maximum num
mand operator’s position DOP. Relay AC oper
35 ates in parallel with lamp I and over contacts 3%
and looks over contacts-ac! independently ofthe
positions to“ the'display circuit.
A circuit is closed’ from earth over-contacts
lsyl, ac3, std, magnet 'BADM' to negativeiand'the
former contacts. Contacts (102. prepare to con - magnet energizes. 'A circuit is‘also closed from
nect an earth to the wire ld leading to the dis ,earth ' over- contacts (104, stE, arc abl, magnet
tributor circuit DDeto release the relay T thereof . ABDM to battery'and this magnet energizes. I At ‘40
when the call is released from theidisplay. C‘on ‘contacts stB a point in the original operating cir
tacts a.c3 prepare anjenergizing- circuit for the cuit for relay AC is opened, but thisgrelay holds
Ymagnet BADM,»and contacts (104 prepare an en > over contacts acl.
Anearth is extended over contacts (102, $153, col,
ergizing circuit for the magnet ABDM. Contacts
' ac5 prepare a circuit for the upper coil of‘relay arc ab3, to relay A short circuiting this relay and
ST and. contacts act prepare a circuit-for the also relay T in the distributor-circuit both of
lower coil of this relay. 'Relay EN also operates
Upon the relapse of relay T in the distributor
over its left hand coil in parallel with lamp I. At
relay S is short circuited at contacts ti
contacts e112 a further point is prepared in the
and relay S releases.‘ A circuit is ‘thereupon
' circuit for relay ST. At contacts enl (see CC Fig.
1) the earth for the normal testing operations of
closed from earth over contacts onl, s5; toot, b4,
all connecting’ circuits associated with the dis
tributor switches‘ so that distributors searching
to close the circuit of the driving motor and the
wipers of the switch are advanced to the home
.50 the relays .T in' the distributors is removed from ‘ magnet LM to battery and the magnet energizes
position where the contacts onl open releasing
are prevented from testing in~whilst callsare 'relay WS which in turn releases relay TCO at: 55
contacts 1086. Upon the relapse of relay TCO the
‘waiting on the display lamps.
The distributor switches D and their associated circuit for the magnet LM is completed over
circuits over which succeeding calls are made contacts tl, sl, tco? and b4 and the wipers are
driven in search of the ‘assigned connecting
are caused. to test into and associate themselves
circuit, and when this is found relay T'operates'
as calls arrive and at their respective contacts-4 from earth over contacts tco'l, ds3, b3, recti?er
for a connecting circuit ‘in response to fresh calls
R, relay T, contacts ws5 and over arc 4 or 4a.
Relay T on operation allows relay S to operate
switch BA, that is, provided meanwhile no calls [and the operations as before ‘described take .65
have been answered. When the maximum num place.
When relay A in the lamp display circuit Fig. 2
ber of calls are queued up on the display lamps,
the circuit for the lamp DOPI and for
. and therefore relay J operated, further search
ing switches test into the lead OF which extends :relay AC is opened at contacts at and a5, and
to the callmeter CM over contacts 9'3 and arcv (1125, relay AC releases. At contacts act and act! the
. and 5 close the circuits for the lamps DOP2--O
over the arcs ab'l—~ab8 and similar arcs of the
the call meter indicating the number of calls so
connected. The resistance in the connection
from each distributor circuit to the lead OF is
individual to the distributor circuit so that the
relays T of other searching distributors are not
affected and can freely test into the lead OF.
circuits for the magnets vBADM and. ABDM are -
opened and the wipers of the switches BA and
AB are stepped. The short circuit is removed
from relay A at contacts ac2. The holding cir
cuit for the upper coil of relay ST is opened at
contacts ac5 but relay ST does not release -im—,;
mediately as it is rendered slow to release by
virtue of its shunted lower coil so that the circuit
to the operator’s circuit is maintained open at
contacts stl for a short period to enable the ap
paratus in the display circuit to function cor
As the call of the ?rst order of priority has been
answered it is necessary that the other calls that
are queued up on the display lamps should all
10 be moved up one in their order of priority.
is accomplished over the arcs ab?, ab‘! etc. It
will be seen that when the switch AB steps a
circuit is closed over contacts bl! and b5, second
contact of arc ab‘! to lamp DOPI and to relay
15 AC in parallel therewith when relay ST releases.
Thus the call of the second order of priority is
moved into the ?rst place, whilst the third call
lighting the lamp DOP3 is moved into second
place and associated with the lamp DOP2 and so
20 on.
When the switch AB steps the circuit to the
lead OF is broken at arc ab5 and the wipers are
stepped on to the contacts connected to the con
tacts a3. Thus all of the T relays in the dis
25 tributors held over the lead OF are released and
connected at contacts call to aa20. Thus an
omnibus operator is called to assist the demand
operators and may answer the calls in an eX
actly similar (manner to that previously described,
the omnibus operator having connecting circuits
associated with the demand distributor circuits.
At contacts aaZl a circuit is closed over the
wire SP for a supervisory device to indicate the
state of congestion to a supervisory operator.
When the number of queued calls fall below eight
relay OM is released releasing relay AA, and the
demand calling lamps on the omnibus position
are disconnected and the incoming lamps re
If however nine or more incoming calls are
queued up on the incoming calling lamp display
on the omnibus position a relay, say OOM sim
ilar to relay OM in LDC associated with that
display will be operated and contacts oomZ will
be open. Thus it will not be possible to inter 20
rupt the incoming 'tra?ic to the omnibus oper
ator’s position until somerof the incoming traffic
has been dealt with.
In order that calls are'not held beyond a cer
tain period during the time that insu?icient calls' 25
the vassociated switches search for the free dis
are in the queue to signal the omnibus position
play lamp circuits, one of the distributors seiz ‘there is associated with each of the relays A—J
ing the circuit of the freed relay A whilst the ofvthe lamp display circuit LDC two relays, such
unsuccessful switches continue in operation un
til they again test into the lead OF over contacts
113, arc'ab5, and the’ call meter CM.
When the operator has dealt with the call the
key CA is restored releasing relays CN and CG
and that portion of the position circuit shown in
35 Fig. 2 is restored to normal.
It will be seen that under normal operating
conditions when no calls exist on the calling
lamps, and relay EN is normal, relay CO is oper
ated on the operation of the key CA and at con
40 tacts col opens a point in the test circuit into
the display circuit.
When seven calls exist on the calling lamps
DOP a circuit is closed for relay ON over its
right hand coil in parallel with the lamp 1 and
relay ON operates and locks over itsileft hand
coil in parallel with- lamp 6. An earth is con
nected over contacts 001122, 0712, to the lead AL
leading to the lamp display circuits on one or
more relief or omnibus positions whereby the
50 operators‘ on these positions are signalled to
assist in the answering of the calls. Relay ON
is released when the number of calls falls below
In the event of nine calls becoming queued up
55 a circuit is closed for the right hand coil of
relay OM in parallel with the calling lamp 9
and relay OM operates and closes at contact cm!
a circuit for its left hand coil' in parallel with
lamp 8.
At contacts omZ a circuit is closed for relay
AA at one_ or more further relief or omnibus
positions, the operating earth being derived over
contacts oomZ which are contacts of a relay sim
ilar to relay OM but which is associated with the
65 display lamps on an omnibus position, so that
if more than a certain number of incoming calls
are signalled in this position the omnibus posi
tions cannot be called to assist in handling the
traffic on the demand position.
Relay AA operates and at contacts cal to aal?
connects the demand display lamps on the omni
bus position OOP in parallel with the display
‘lamps on the demand position so that the, corre
sponding lamps‘ light. The circuits for the in
75 coming lamps on the omnibus position are dis
as relays SA and?ZA, only those relays asso
ciated with the relay A however being shown, the 30
other pairs being connected and operated in an
' identical manner.
Two contacts a6 and a1 control the operation
of the relays SA and ZA, and as all of the other
relays B—J are provided with similar contacts,
which however are not shown, the relays are
designated as having seven contacts.
‘ Earthed impulses are periodically and alter~
nately delivered over the leads S and Z.
Assuming that a call is held on relay A over
a period during which the impulses, are delivered 40
to the leads S and Z,’then, when the impulse is
given over the lead S a circuit is closed for the
right hand coil of relay SA over contacts 2112 and
a6, and relay SA operates, and looks over its left
hand coil, contacts a'!, left hand coil of relay ZA,
and contacts sal. Relay ZA will not operate in
this circuit. When the impulse occurs over
lead Z relay ZA operates over its right hand
and contacts 8112. At contacts zal a locking
cuit is closed for relay ZA over its left hand
and the left’ hand coil of relay SA is short
coil 50
cuited making the relay slightly slow to release.
The circuit for the right hand coil of relay SA is
opened at contacts zaZ and after a short period
relay SA releases. A circuit is closed for relay
DL at contacts 203, and relay DL operates.
At contacts all! a circuit is closed for relay AA,
and at contacts (H2 an earth is applied to the lead
AL to operate similar relays such as AA on the
relief positions.
The switches AB and BA are stepped in the
manner described to alter the position of the
calls in the queue until the switch AB is stepped
to the twenty ?rst contact whereupon a circuit
is closed from earth over contacts abdm, arc and
wiper ab‘! magnet ABDM to battery and the
switch AB is stepped to its normal position under
theccontrol of its interrupter contacts.
diately the wiper of are (1112 steps out of align
ment with the wiper of arc bal relay SY releases
and at contacts syl closes the circuit for magnet
BADM and the switch BA homes whereupon re
lay SY operates and opens the homing circuit
for magnet BADM at contacts syl.
The common relays NA in the lamp display cir~
cuits are night alarm relays adapted to operate
when any lamp is alight to operate an alarm.
We claim:
1. In a telephone system, a group of connec
tive circuits, a group of hunting switches of the
homing type having access to said circuits as
?rst choice, a group of over?ow circuits accessi
ble to said switches as second choice, whereby
10 switches operated at times when no connective
circuits are available will connect with successive
over?ow circuits, and controlling means operat
ing on switches connected with over?ow circuits
in the order in which the connections are estab
lished for releasing a connected switch and for
causing it to rehunt over said connective circuits
each time a connective circuit becomes idle.
2. In a telephone system, a group of individual
over?ow circuits, automatic switches having ac
cess to said circuits if no regular outlets are
available, means for making each individual over
?ow circuit busy when seized, a common over?ow
circuit which is not made busy when seized and
which may therefore be occupied by a number of
iv 111 switches when the individual over?ow circuits are
all busy, means for successively releasing the
switches connected to individual over?ow cir
cuits, and means effective whenever an individual
over?ow circuit is freed for causing the switches
connected to the common over?ow circuit to hunt
for the free individual over?ow circuit.
3. In a telephone system, a group of automatic
switches, a group of connective circuits accessible
to said switches,v a group of individual over?ow
circuits accessible to said switches only if none
of said connective circuits are available, a com
mon over?ow circuit accessible to said switches
only if all said individual over?ow circuits are
busy, means operative at a time when one or more
40 switches are connected to the common over?ow
circuit and responsive to a connective circuit be
coming available for releasing one switch con
nected to an individual over?ow circuit and for
causing it to hunt for the available connective cir
r cult, and means for releasing all switches con
nected to said common over?ow circuit and for
causing them to hunt for the free individual over
?ow circuit.
4. In a telephone system, a group of over?ow
50 circuits, at corresponding group of lamps, switches
having access to said circuits, means for busying
each circuit when seized and for lighting the cor
responding lamp, means for releasing switches
from over?ow circuits one at a time, and means
intervening between the said circuits and lamps
and operative every time a switch is released for
changing the relation between said circuits and
said lamps to associate each circuit with a dif
ferent lamp.
5. In a telephone system, a group of relays
numbered consecutively, a group of lamps cor
respondingly numbered, means for energizing
said relays in the order of their numbering to
light the corresponding lamps, means for releas
ing said'relays in the same order, and means op- ;;
erative each time a relay is released for shifting
each relay into association with the next lower
numbered lamp.
6. In a telephone system, a plurality of con
nective circuits common to a plurality of opera it)
tors, automatic switches having access to said cir~
cuits, circuit arrangements such that the con
nective circuits are normally unselectable by said
switches and are individually made available for
selection when the operator handling the calls *
is ready to take a call, over?ow circuits accessible
to said switches at times when no connective cir
cuits are available for selection, and means re
sponsive to a predetermined number of over?ow
circuits becoming occupied for automatically sig
nalling another one of said operators to assist in
handling the calls.
'7. In a telephone system, a plurality of connec
tive circuits common to a plurality of operators,
automatic switches having access to said cir- .2.)
cuits, circuit arrangements such that the con
nective circuits are normally unselectable by said
switches and are individually made available for
selection when the operator handling the calls is
ready to take a call, over?ow circuits accessible
to said switches at times when no connective cir
cuits are available for selection, means for suc
cessively releasing switches from over?ow cir
cuits to permit them to hunt for connective cir
cuits as the latter are made available by the op
erator, and means for automatically signalling
another operator if a switch remains connected
to an over?ow circuit for a predetermined time.
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