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Патент USA US2405194

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Aug., 6„ E 4°
Filed _July 2o, 1945
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/fv VEA/Tops“v4.w»
Aug» 6, 1946«
...L> w. DEHN ETAL."
Filed July ép, 194sv
4 sheets-sheet 2
Aug. 6, 1946.
Filed July 20, 1945
4 Sheets-Sheet -1'?,
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Patented Aug. 6, 1946
Joseph W. Dehn, Great Neck, and Myron C;
Goddard, Garden City, N. Y., assignors to Bell
Telephone Laboratories, Incorporated, New
York, N. Y., a corporation'of New York
Application July 2o, 1943, s_e?iai No. 495,489
(Ci. 179-18)
7 Claims.
This invention relates to telephone systems and
particularly to those in which connections are
established by automatic switches.
In automatic switching systems using line find
ers or trunk finders it is usual to have a plurality
of such :ñnders in groups serving groups of lines
or trunks.
Associated with. each finder group is -
a start circuit actuated by a line or trunk over
‘ improve the flexibility of group allotting arrange
ments in automatic switching; systems in which
there is a tendency to limit the operation of
mechanism to a single channel during light load
A feature of the present invention consists in
automatically operable preference control mech
anisms for shifting the Vpreference for selecting
which a call has been initiated and this start
finders arbitrarily during light load calling peri
circuit energizes a particular iinder except when 10 ods and in a sequential order during busy load
this finder is in use. When the ñrst finder is in
Y calling periods.
use it transfers the start lead to the nextfinder
Another and related feature of the invention
of the group. The start lead is thus transferred
consists in means associated with the preference
to the next in order finder in a group or sub
control mechanism automatically operated by
group in a sequential manner by the preceding
periodic switching operations >in the office for
finder as the finders are taken for use.
» ¿_ determining kwhen the order of preference for
In the system disclosed herein both line finders
trunk finders and senders shall be normally ad
and trunk finders are used, each having other
vanced and when it shall be arbitrarily advanced.
mechanisms permanently connected thereto, the
These and other features will be discussed more
line finder having a trunk’and a dual selector 20 fully in the following description as illustrated in
connected thereto and the trunk finder having a
the accompanying drawings in which:
sender connected thereto. This arrangement is
Fig. 1 .illustrates a line finder, a line-finder
selector trunk, a Vdual selector, and associated
selectors and villustrates in detail the mechanism
used as a matter of economy to obviate the use
of links or connectors between the finders and
the senders and for the sake of speed in operat 25 of'a-trunk-finder circuit; Y
ing these mechanisms.. Both a line finder and
. Fig. -2 illustrates the mechanism associated with
a trunk ñnder are automatically energized by an
a number o_fsubgroups of trunks Aand trunk-finder
incoming call, the line finder hunting for the
circuits for _shifting the preference of trunk-`
calling line and the trunk finder hunting for the
findercircuits in a sequential order as the finders
trunk permanently connected to the hunting line 30 are taken for use; _ _ _
finder. Thus a sender is automatically connected
.'Fig. 3 illustrates anY automatically operable ar
with the calling line in a short space of time by
rangement for arbitrar-ily shifting the preference
the action of the line and trunk finders. The
of trunk iinders during -light _load calling periods
circuits from the sender dial tone mechanism
and for placing the :ñnder preference mechanism
and dial pulse responsive mechanism extend 35 in the normal sequential order during busy load
through the trunk finder, the trunk circuit, the
calling periods; and
line under and over the line to the station mech
Fig,` 4 illustrates the grouping arrangement of
line finders, trunks, selectors and the trunk find
anism of the calling subscriber.
One group of lines is served by a particular
group of line finders and a plurality of groups 40
of trunks connected to these line finders is served
ers and the senders. _ _»
General description
by'a particular group of trunk finders. A start
circuit for energizing the trunk ñnders is com
of an automatic switching system in a small tele-A
mon to the trunks of a group and also common
phone vareafo'r which this invention is used is
The grouping arrangement of the mechanism
to the finders of this group which serve these 45 shown in Fig. 4.
The finders are operated in a set se
Reference may be had to my
copending application, Serial No. 495,487, filed
July 20, 1943, for a complete descriptionof differ
quence during busy periods as the finders are
taken for use. However, during non-busy periods
ent units of mechanism shown herein in dia
if calls come into the ofñce from a given group
grammatic form and also for a completedescrip
of lines over spaced periods and each call is dis 50 tion of the organization and operation of these
connected before another call comes into the office
units of mechanism.v Two groups of lines 400
the same finder would be used for all of these
and 4H are shown served by two subgroups of
successive calls. In the case of the trunk finders
line finders each of which may comprise ten line
which each have a sender permanently connected
finders. The ten line finders dill-402 have ten
thereto this would mean that the same sender 55 trunks M13-404 and Aten dual selectors 405-406
would be'repeatedly connected to the calling lines
permanently connected thereto’.
of a group if the calls in the group were spaced
apart so that each switching connection is com
pleted and disconnected before another call from
this group of lines enters »the oiiice.
The same ar
rangement is used for each subgroup'as shown
for' the :ten line finders 4i8-4I9 which served
the group of lines 4H and -have- ten trunks 420
nl.The object -of thisrinvention is, therefore to _
42| and ten .dual selectors 422-423permanently
connected thereto.Y »The sequence of operation of
line finders in a subgroup of li-ne'iinders is well
known inthe art and therefore only 'a general
description of this operation need be given. The
energization of line equipment responsive to an
incoming call actuates what is known as a group \
start relay which energizes a line iinder and marks
a segment on the line-finder commutator to guide
the line finder to a particular level >of* switch tter
permanently connected thereto. -.As an example,
let it be assumed that during a light load period
the first trunk ñnder 4I2 of a subgroup is ener
-. gized repeatedly by successive calls because these
calls .are spaced so that there is only one call
` in the subgroup alt any one time.
Since a sender
426 is permanently connected to this trunk ñnder
' this sendervwill be continuously used to the ex
clusion of the other senders and if this sender
minals where the calling line may be found. '- The
becomes faulty in its operation it may prevent
line iinders are allotted for use in -`a 4sequential 10
completing a number of telephone connections.
order depending upon the busy `condition of the
An auxiliary preference shifting mechanism is
line iinders in the subgroup. This allotting is
shown in- Fig. 3 which is automatically respon
controlled by the transfer of the line-finder start
sive to light and heavy load conditions. During
circuit sequentially as the finders become busy
normal heavy load conditions this mechanism
which circuit` is carried through contacts of a
causes the regular sequence starting mechanism
relay in each line iinder.
to function as described above but during light
In the presentlsyste'm the operation of a line
periods when calls are' spaced apart it alters
finder such -as 40| .fromy its start circuit auto
fthe. preference for thev trunk finders after each
matically energizes mechanism in its associated
call and thus alters the preference for senders
trunk 403 which establishes a start circuit for a 20
connected to these trunk finders. This not only
trunk -iinder so that both the-line finder and the
has the advantage of using different sender mech
trunk Afinder are hunting simultaneously. The
anism for successive calls but has the advantage
line iinder 60| hunting for the calling line and
the trunk finder, Figs. 1 and 2,-hunt for the trunk . of providing telephone service at all times even
403 connected to the hunting line îñnder 40|. 25 though a sender mechanism _is faulty in an un
attended oiiice.
The trunk-iinder start circuitis common to the
line ñnders and associate-d 'trunks of the line iind
Detailedv description
er subgroup as shown‘and thereforefany trunks
One of a group of lines is shown in Fig, 1 con
in this-subgroup will `establish a start circuit for
to a subscriber’s station‘A which causes
subgrouprstart relay` 4|4. Likewise any trunk in 30 nected
the energization of a line ñnder and line iinder
a second group 420-42Iwi1l establish» a circuit
selector trunk circuit such as |00 and IílI respec
for group» start relay’ 4I3. Each start relay con
tively when the subscriber A removes the receiver
trols a subgroup of trunk finders.
from the switchhook. The line ñnder and line
Trunk iinders 4I I-4I2 are diagrammatically
selector trunk circuit operate in a manner
shown for serving theiirst subgroup of trunks 35 ñnder
fully .described in copending application Serial
and trunk iinders- 4 I 5 and-4 I 6 for serving the sec
No. 495,487, filed July 20, 1943, and therefore need
ond subgroup of trunks, each of these trunk lind
not be described herein. VThe energization of the
ers being the same as shown in'Fig. l of the draw
line finder |00 by a subgroup start relay also
ings associated With the sequence circuit and sub
group start circuits of Fig. 2. A 'shown diagram 40 causes the energization of the line finder selector
trunk IUI which connects ground to the start lead
matically in Fig. ‘4, -thel’operation `of `'subgroup
|45 for energizing trunk ñnder subgroup start
start relay 4I4w-i11 actuate trunk finder 4|2 if
relay 203. Four such relays are shown 200, 20|,
it is idle and if Ait is busy will actuate trunk ñnder
202 and 203 for four subgroups of trunks and
4I I or another trunk finder in the subgroup and
therefore for four subgroups of trunk iinders.
at the same time will mark a commutator seg
As shown in Fig. 4 the start lead |45 and there
ment for guiding the trunk ñnder. As previously
fore the start ground relay 203 are common to all
stated each‘trunk -ñnder `has a sender perma
trunks in a subgroup. The operation of relay 203
nently connected thereto and therefore the send
is shown for connecting íground to segment I of
er 426 is connected through the trunk to the call
ing line when the trunk finder-412 is actuated. 50 commutator |22 and for energizing relay I32 of
the trunk ñnder which latter circuit may be
Sender 421 may be connected through the trunk
from ground on'contact I of the start
to the same calling lline when trunk ñnder 4II
ground relay 203, contactl of relay 205, contact
is actuated because trunk cfin1deri4l2 is in use.
2 of jack 233, lead 25|, contact 3 of relay |35
This may be any trunk of the group which actu
winding of relay I32 to battery. If this trunk
ates the trunk finder for associating a sender
is busy and relay |35 of this trunk ñnder
throughÍ the trunk to the line. The second and
is operated the ground from contact I of start
other groups of line ñnders, trunks, trunk finders
relay 203 extends to the ’next sequential trunk
and senders are Aoperated and associated together
finder 245 for operating a relay the same as relay
as outlined for the ñrst group.
From the foregoing it may be seen-that the 60 I32 in the latter trunk ñnder. This circuit would
extend from contact I of relay 203, Contact I of
normal sequence of operating finders is econom
relay 205, contact 2 of jack 233, contact 3 of relay
ical 'for'all automatic switching oiiîces and' would
|35 operated, contact 2 of relay |26 thence over
not> require any auxiliary transfer devices in a
large o?ce in which more than one ñnder is nor
lead 253, contact 3 of jack 233, contact 2 of jack
mally in use. However, in smaller telephone
areas there are periods when incoming calls over
lines- in a group are spaced apart and the ñrst
trunk finder is the same as relay |35 in the first
ñnder in a subgroup is taken for use on each
incoming call over this period of light load. In
the case of the present automatic switching sys
tem such as is fully described in copending patent
application," Serial No. 495,487, íiled July 20, 1943,
234, contact of relay 26, to a relay such as relay
|32 in trunk finder 245. Relay 206 in this second
ì trunk finder of the subgroup.
'The‘sequence circuit or preference circuit for
otherv trunk ñnder subgroups is shown in Fig. 2.
Relays 201 and 208 are in an intermediate sub
group of trunk finders and are the same as relay
|35 shown in Fig. 1. lRelays 209 and 2|!)A are in
another intermediate'subgroup and relays 2| I and
overwerk particular trunk‘ñnders 'and senders 75 2 I2 lare in the end subgroup. VStart ground relay
and particularly to this system when used as an
unattended «oñice this normal procedure would
' 6
200 operates from a start circuit common to one
subgroup of trunks and extends this start ground
through the mechanism of the subgroups of trunk
finders represented by relays 2|| and 2|2. Relay
20| energized by the start circuit of another sub
group of trunks extends its start circuit through
the group of trunk finders represented by relays
209 and 2|0. Relay 202 extends its start circuit
upper winding of relay ’|36V to batteryv on contact
5 of relay |35. This holds relay ‘|36 in an oper
ated position to prevent further- stepping. Relay>
|26 is made slow in operating to give a short time
interval between the last ,vertical step and the
first rotary step which is brought about by the
operation of relay |26. Relay |26 locks through
its lower winding in series with the vertical mag
to the subgroup of trunk ñnders represented by
relays 267 and 208 as shown. Relay 203 extends 10 net to battery on contact 5 of relay | 35. This
places relay |26 under the control of relay |35
its start circuit to the subgroup represented by
and causes its release when relay |35 operates.
the trunk ñnder in Fig. 1 and the trunk finder
The operation of relay |26 transfers the stepping
represented by relay 206. These relays 200 to 203
circuit from the vertical to the rotary magnet.
also connect ground to segments of commutators
in the respective trunk ñnders depending upon 15 'I'his circuit may be traced from battery through
rotary magnet |30, contact 4 of relay |26, con
which trunk ñnder is energized, By reference to
tact of relay |36 to ground on contact 2 of relay
diagrammatically grouped units shown in Fig. 4 it
| 32. The rotary magnet thus lsteps the shaft
may be seen that the operation of start ground
around until the sleeve wiper |51 reaches a ter
relay 4|4 representing a relay such» as 203 mayr
associate ground from its contact I with any corn 20 minal whichis connected to battery through-the
winding of a cut-off relay in the trunk circuit
mutator segment of the trunk ñnders in the
group. When trunk finder 4| 2 is energized by
relay 4|4, the trunk ñnder is arrested in its mo
tion when it reaches the ñrst level of terminals.
These terminals _are indicated as terminals 409. 25
When trunk iinder 4| I is energized by relay 4|4, it
is arrested on the second row of terminals indi
cated at 4|0 since the ground from contact I of
connected» to sleeve lead |50. This circuit extends
from ground on contact 3 of relay |32, lower
winding of‘relay |36, contact 2 of relay |35, re
sistance |2|, upper winding of relay |20, sleeve
brush |51 to battery through the cut-01T relay
winding in the trunk circuit. The trunk circuit
cut-01T relay operates in this circuit and in so
connects ground with the sleeve lead |50
start relay 4 I 4 is connected to the second segment
in place of battery. Relay |36 is thus held op
of the commutator of trunk finder 4| I. .
The trunk ñnder shown in Fig. 1 operates in 30 erated to prevent further stepping of the brushes
in a rotary movement. Relay |20 is also suffi
the following manner for connecting a sender to
ciently operated to close its contact 9. 'I'his ener
the calling line. For this connection it may be
gizes the lower winding of relay |20 over a circuit
assumed that the trunk ilnder shown Ain Fig. >1extending from battery through this winding and
is used and that therefore the start circuit is
contact 9, contact | of the rotary magnet, con~
extended by relay 203 through contact 3 of relay
tact of relay |36 to ground'on Contact 2 of relay
|35 and the winding of relay |32 operating the
|32. The operation of relay |20 connects leads
latter relay, and that segment I of the commuta
to |49 and |5| to |53 directly to the mecha
tor |32 is connected with ground by the operation
of relay 203. Relay |32 associates ground with 40 nism of sender 320 and establishes an operating
circuit for relay |35. This operating circuit may
the sleeve lead ||| extending to the sender and
be traced from battery through the upper winding
operates the stepping relay |36. The circuit for
of relay |35, contact I0 of relay |20 to ground on
operating relay |36 may be traced from ground
contact 2 of the olf-normal contacts |25. The
through contact 2 of relay |32, contact of Vertical
magnet |3|, Contact 2 of rotary magnet |30, up 45 operation of relay |35 closes _the sleeve lead
ground from the trunk to the sender which may
ped winding of relay |36 to battery connected to
be traced from ground on sleeve lead |50, brush
contact 5 of relay |35. The stepping relay |36
|51., contact 4 of relay I 20, contact 2 of relay |35
establishes a circuit for the vertical magnet which
to sleeve lead ||| extending through the sender.
steps the shaft up one step placing the 'commuta
tor brush |23 on the first segment. l'I'hecircuit 50 Relay |35 also closes a locking circuit for relay
|20 traced from battery through its lower wind
for the vertical magnet may be traced from bat
ing and contact 9 of relay |20, contact 4 of relay
tery through contact 5 of relay |35, vertical mag
|35 to sleeve lead |||. Relay |35, as has been
net |3I, contact 4 of relay |26, contact of relay
previously described, transfers the start lead 25|
|36 to ground on contact 2 of relay |32. The
vertical off-normal springs |25 are closed and the 55 to the next in order trunk ñnder. The start lead
extends from lead 25| through the associated
circuit for relay |36 is opened by the contact
armature, contact 2 of relay |26, lead 253, contact
of the vertical magnet |3I. Relay |36 releases
3 of jack 233, contact 2 of jack 234, through the
which causes the release of the vertical magnet
contact of relay 206 to a relay the same as relay
which now recloses the circuit to relay | 36. If
brush |23 is not associated with-ground on the 60 |32 of the preceding trunk ñnder. 'I'he opera
tion of relay | 35 removes battery through its
ñrst terminal, relay C and the vertical magnet
contact 5 from the upper winding of relay |36
continue to step the brushes ofthe trunk ñnder
and from the vertical magnet circuit and relay
in 4an upward movement until the commutator
|26 and also releases relay |36 by short-circuit
brush reaches the segment which is grounded
by the operation of the group start relay which 65 ing its lower winding through its contact 2. This
releases relay |26 so that the start circuit may
in this case is relay 203. Since, for this exam
extend through its contact 2. The circuit for
ple, segment | of commutator |22 is connectedrelay |32 is opened through the continuity con
with ground, the brushes |54 to |6| of the trunk
tact 3 of relay |35 and relay |32 is made slow
finder are arrested on the first level of terminals.
to release so that ground is'held on the sleeve
A circuit fory relay |26 is established through its
lead extending to the dual selector and the sender
upper winding in series with the upper winding
until a short period of time has elapsed so that
of relay |36. This circuit may be traced from
the mechanism of the associated circuits has had
ground on contact 2 of relay 203, segmentl >of
commutator |22, brush |23, upper windingof
relay | 26, contact 2 of the rotarymagnet-|36.;-
time to function.
The sleeve circuit in the trunk |0| has ground
extended thereto, ñrst, by the line länder,B_.ndsec-y
ous' senders maintains -relay 30|‘constantly oper
ated` and .the normal preference circuit shown in
0nd,.' by aïrelay in they dual. selec-.tor~ |02. `When
this 'ground is initially- connected iîrorrr'the- line
li‘igfZ1 for the trunk‘ñnders is in use so that when
one îiinder is busy the next in order finder in the
sequence is energized in the Vmanner previously
the trunk liinder’ andïat the same time‘connects
finder to the trunk" circ >'t, a' 'trunk start relay-is
operated which establishes -the’start circuit? for
battery through the> winding of the trunkY cut
off Vrelay Wi'thïthe sleeve lead |50 extending to the
sleeve terminal of the Vtrunk` finder terminal-bank.
As previously described fwhen "theV 'trunk finder
ñndsthis terminal, relay '|20 »is operated'suñl
ciently »to close 'its contact 9. 'This operation takes
pla‘ce‘through the 'upper winding of relay |20,
During light load periods when the incoming
calls are spaced apart and only one sender is ener
gized at' Va time Y'the following procedure takes
10 place .in the `ñnder preference control circuit as
follows. During vthis period the ñrst sender ener
gized operates its relay 32| which connects
ground through the winding of relay 30| which
operates. Relay 322 is operated to release the
sender. The latter relay holds'ground through
lower winding of `relay |36 to' ground on contact 3
of relay |32 and when this circuit is established
the cut-off >relay in the trunk is operated in such
a manner as to connect -ground instead of-battery
with ïthe sleeve -lead |50 and relay |20 -is «locked
through its lower winding as described. The
ground extends over lead |50 through contact 4 of
relay >|20 and contact 2 of relay |35 after the 'i
latter relay is operated, thence over -sleeve llead
||| tothe sender for holding the off-normal
ground sender relay 32| 'and' as noted on the
drawings the operationl of relay 32| operates relay
324. The energization of -relay |32 in the trunk
the winding of relay 30| until the sender has re
leased- which releases both relays 32| and 324.
Relay 322 is slow to release after the other mech
anism of the sender has been released and there
fore .the release of -relay 324 causes a circuit to be
established from’ground through contact 2 of re
lay 322, contact of relay 324, contact of relay 323,
contact 2’of relay 30 I, rotary :magnet 304 to bat
tery energizing the rotary> magnet 304.l The
sender having released causes the release of relay
322 thus removing ground from rotary magnet
304; removing ground from the winding of relay
30| and contact 3 of relay 302. When ground is
removed from the rotary magnet'304 the brush
finder causes the operation of off-normalrelays
32| and 324 so that the sender is prepared to func
tion 'as soon as it is connected Vto the trunk cir
308 steps from its normal position to terminal |.
The removal of ground from the winding of relay
cuit and line‘finder. This automatically ‘estab
lishes the dial tone >circuit and Vcauses dial tone
to be connected with conductors extendingrto "the
33|and from'armature 3 of relay 302 causes a cir
cuit to be established for‘ relay 302 from battery
subscriber’s line and thereafter establishes a con
through resistance 3| I; winding of relay 302, con
nection between vthe calling subscriber’s line and
tact V3 of relay 30| to ground on contact 2 of relay
pulse responsive equipment in the 'sender for set
ting the ’sender according to dial pulses trans 35 309. Thus, both relays 30| and 302 are operated.
mitted by the calling subscriber.
l Y Y
The ñnder preference control circuit j 300 is
shown connected to one sender rcircuit 320 and
it is also -'shown that this control circuit is corn
mon to all senders of the telephone office. Since
each trunk ñnder has lasender permanently con
nected. thereto the device 300 is a sender prefer
ence‘control circuit as well as a trunk-finder con
trol circuit but'will be known hereinafter as the
The operation of relay 302 establishes a circuit to
arbitrarily change the preference lof all trunk
ñnder circuits by operating relays 204 and 205.
It will now be apparent that if start ground re
lay 203 'is'energized the start circuit extends 'from
ground on contact I of relay 203 through the in
ner contact | of relay 205, contact 2 of jack -234
to trunk iinder Y245 which -is the second trunk
finder in the sequence of the start circuit. Like
Wise ifany of >relays 200, 20| -or 202 are energized
the start circuit extends to the second trunk
the copending application, Serial No. 495,487,
ñled'July 20, 1943,'may be had for the detail oper
finder of the subgroup instead of the first trunk
finder. `By vreference to Fig. 4 it will be seen that
ation of the senders shown diagrammatically in
Figs. 3 and 4. For convenience in referring to 50 the second :trunk iinder 4| l `has sender 421 per
the larger disclosure, relay numbers-'are shown
manently connected thereto whereas the ‘ñrst
in the sender 320 in brackets which are the 'same
trunk finder 4|2 has sender 426 permanently con
as the numbers given to these relays in the afore
nected thereto. Therefore, in shifting the prefer
mentioned copending patent application, the
ence of the trunk finder arbitrarily as above-out
numbers which are not »in brackets will be used 55 lined the preference is shifted Vto a different
in this description. The control features ofV the
sender than would be used if this preference had
finder preference control circuit. Reference to
mechanism of the ñnder preference control' cir
cuit 300 depend upon the frequency with which
senders of the oilice are taken `for use by incom
ing calling-lines. The‘energiaaticn of relay 32|
not been altered. The rotary oft-normal contact
336 is closed when brush308 steps to the iirst
terminal and with both relays 30| and 302 oper
ated a circuit is established for release magnet
when thev sender is taken for use, establishes .a 60 335 :from ground on contact | of relay 30|; This
circuit >for relay 30| from ground on `the contact
causes the brush 308 to restore to its normal posi
of relay 32|, contact | of relay 303, contact 3 and
tion but ydoes not cause the release of either 're
winding of relay 30|, resistance 3|0 to battery.
lays 30| or 302.
This ground places a shunt on relay 302 through
When the next trunk finder and sender are
its contact 3 so that relay 302 does not operate 65 taken for use relay 132| of this sender is oper
atthis'time. The operation `of relay 324 opens
ated which again connects ground to lead 330
which in vthis case short-circuits the winding of
relay 30| causing its release. Relay 302 is, how
ever, held operated from ground over lead 330,
the rotary magnet 304 is energized `and deener
continuity contact 3 of relay 33| released, wind
gized and requires. the lenergization. of release
ing of Arelay-332, resistance 3|I to battery. This
magnet 305 >to return it to its normal position.
trunk liinder and sender are the second preference
During normal busy load periods more than-one
finder and sender since relays 204 and.205.;are
sender is in constant useY and -?thereîorej-the 75 operated. «Uponlthe-operation of? relay322 for
a circuit at one point which is later established
for the rotary magnet 304 of switch 301. Switch
301 is of the type which is moved `one step when
`the release of this sender and the release of relays
32| and 324 a circuit is again established ’over
lead 33| for the rotary magnet 304. In this
case the circuit extends through contact 3 of
relay 302, rotary magnet '304 to battery. When
relay 322 releases, the brush 308 again steps from
its normal position to terminal | and, since the
cessive sender operated vand released-on overlap
ping calls associates `ground with the stepping
circuit for energizing rotary magnet 304 and the
switch is advanced as each sender is released.
The circuit for energizing the rotary magnet 304
is over conductor- 33|. Assuming that relay 30|
is operated this circuit extends from contact 2
ground is removed from lead 330, the circuit for
of relay 32-2, contacts of relays 324 and 323, lead
relay 302 is opened and the latter relay releases.
This constitutes the ñrst cycle of preference 10 .33| to Contact 2 of relay 30|, rotary magnet 304
to battery. Upon the release of each sender
shifting by relays 30| and 302. The release of
this circuit is closed and opened causing the
relay 302 returns the sequence circuit shown in
switch to advance one terminal. Under this con
-Fig. 2 to normal by releasing relays 204 and 205
dition if the switch advances to terminal 6 re
and thus the first trunk finder is the preferred
finder for the next successive call.v The third 15 sponsive to the operation and release of six
consecutive senders without any spaced periods
spaced call which is the next successive call
in the operation of 4these senders, relay 309 is
again operates a sender relay 32| causing- the
operated from ground connected to brush 30S.
operation of relay 30| and the release of this
309 in operating establishes a locking cir
sender brings about the operation of relay 302
and the operation of the rotary magnet 304 20 cuit to ground on contact | of relay 32| _of the
energized sendersl so that the continuous over
causing the brush 308 to step forward. The
lap operation of 'senders maintains relay 309
operation of relay 302 _again shifts the sequence
locked in an operated position. Relay 309 in
circuit by the operation of relays 304 and 305
operating opens the circuit extending over lead
and the release of relays 30| and 302 by the sub
sequent operation and release of a sender again 25 330 to relays 30| and 302 and opens the ground
circuit from its contact 2 which is used to oper
shifts sequence circuit of the trunk finders as
ate relay` 302 as previously described. This
explained. When the switch 301 moves away
causes the release of relay 30| establishing a
from its normal position, the rotary oñ-normal
circuit for restoring switch 301 to normal by
contact 306 is closed and therefore, at any time
that relays 30| and 302 are both operated or 30 energizing the release magnet 305 'and prevents
any further arbitrary shifting as long as there are
both released, the release magnet 305 is energized
overlap operations of the senders. If relays 204
through contacts 2 of relays 302 to ground on
and 205 were operated they are now released and
contact | of relay 30| and therefore this switch
the normal 'sequence operation as shown in Fig.
is released very often during calls which'are
spaced apart. In fact, this release occurs after 35 2 remains in use as long as this busy condition
ensues. The next light load period when thelast
each cycle of operation when relays 30| and 302
sender in use has released and no other sender
are both operated or both released for shifting
of the office is in use for a switching connection
the preference circuit of Fig. 2. However, when
removes ground from lead 330 and the locking
a busier period occurs the switch may advance
a number of steps without having the trunk 40 circuit for relay 309 is thus open and this relay
now releases. The next sender operated will
finder preference shifted.
thus operate relay 30| >and if a spaced light load
Let it be assumed now that after a number
period 'follows the busy period, the arbitrary
of spaced operations of the switching equipment
shifting of ‘the preference again takes> place
of the oñice including senders, when only one
switching equipment is operating at one time, 45 under the control of relays 30| and 302 as oper
ated. by the spaced operation of the senders.v
a busy period occurs and that there are a num
Frequently, during light load periods three .or
ber of over-lapping calls and therefore that more
than one sender is in operation at one time for
four calls may enter the office in an overlapping
order and thereafter the calls> may be again
completing switching connections. These over
lapping operations hold ground continuously on 50 spaced apart. During this period when more
than one sender is in operation at the same time,
lead 330 since a relay the same as relay 32| is
relay 30| or relay 302 would .remain .operated
operated in more than one sender and the oper
and the other relay of this pair would remain
ation of relay 32| in one sender overlaps the
normal. Each of the four senders during.. this
operation of relay 32| in another sender. If
relays 30| and ‘302 are normal, the ñrst sender 55 overlapping period would, upon releasing, ad
vance switch 301 one step so that at the time the
operated during this busy period will operate
fourth sender released'brush 308 would'have
relay 30| and place the shunt ground on contact
reached the fourth terminal. Assuming that re~
3 of relay 302 to prevent the operation of relay
lay 30| had been operated during this' overlapping
302. If relays 30| and 302 are operated, the
first sender operated during the busy period will 60 period, relay 302 is operated at 'the time of re
leasing the fourth- sender by removal of ground
release relay 30| by placing a ground shunt
from lead 330 which removes the shunt from re
through contact 3 of relay 302. This will con
lay 302. This voperates relays 204 >and 205130
tinue until such time as all of the senders in
arbitrarily shift the preference of the trunk
operation at any one time have released and the
and Vassociated senders. On the other
preference for the trunk finders and senders will 65
hand if relay 302 was operated during kthe over
be according to the position of the relays in the
lapping period ‘and relay 30| was released, then
finder preference control circuit 300, that is, with
the release of the fourth sender would cause the
relays 204 and 205 operated, the second finder
release of relay 302. In either case both of relays
and associated sender are preferred and with
relays 204 and 205 released the first trunk finder 70 30| and 302 wouldv either be operated or released
and consequently a circuit is established for the
and associated sender are preferred. This, of
release magnet 305 to cause Athe switch 301g`to
course, depends upon whether relay 30| is held
restore to normal. Therefore at this> time the
operated at the time or whether relay 302 is
normal shifting arrangement of preference shown
held operated.
During this temporary busy4 period each suc 75 in Fig. 2 is >not used sincev the light load’period ,
of 'incoming calls continues even'though’iîor'a-
short period a small number of calls enter the
ofiice in overlapping order.
ating a finder, the lines of. each group preferring
said finders in a particular order, mechanism for
normally advancing the order of preference se
quentially as said finders and senders are taken
`From thel foregoing it is vaplîlarent that’ the
auxiliary device 30D is common to and under con
trol of thev senders in the. oflice for arbitrarily Ul for use during busy load calling periods, an aux
iliary device common to and under thel control of
switching the order of preference of trunk iinders
the senders in said ofñce for arbitrarily switching
and senders during light -load calling periods on
said order of preference during'light load calling
each occasion after the release of the sender when
no sender in the oñice is in use for a switching
connection so that the senders serving each group
of lines are used in successive order during light
load periods but automatically control the re
version to the normal preference shifting con
trol shown in Fig. 2 during heavy load calling
periods on each occasion after the release of a
Isender when no other sender of the oliice is in
use ‘for a switching connection so that the send
ers serving each group of lines are used in a suc
cessive order during light load periods and a con~
trol mechanism automatically operated by' peri
odic sender operations in said office for deter
What is claimed is:
l. In an automatic switching telephone oflice,
, mining when the order of preference for finders
and senders shall be normally advanced and when
switches, groups of lines, a plurality of senders, a
it shall be arbitrarily advanced.
plurality of iinders in groups each having one of
said senders permanently _connected thereto op
flce, groups of lines. a group of line iinders serv
erable for connecting said senders to said lines,
means responsive to a call overa line for operat
ing a finder, the lines of each group preferring
5. In an automatic switching telephone oi
ing each group of lines. each line ñnder having
a trunk permanently connected thereto, senders.
a group of trunk iinders common to each group
of line finders and trunks, each- trunk iinder hav
saidiinders in a particular order, mechanism for
normally advancingr the order of preference, se. 25 ing one of said senders permanently connected
thereto, means responsive to a call over a line
quentially as` said finders and sender-sare taken
for operating aline finder and a trunk finder for
for use during busy load- calling periods and an
connecting a sender to thev calling line, said trunk
auxiliary device for arbitrarily advancing said
finders and senders being operated in a preferred
order of preference during light load- calling
30 order, mechanism for normally advancing the
order ot> preference sequentially as ysaid trunk
2. In an. automatic switching telephone, office.
iinders and senders are taken for use-during busy
switches, groups of lines, a plurality of'Y senders,
load calling. periods, an auxiliary device for ar
afplurality of finders in groups each having one
advancing said order of preference dur
of said senders permanently connectedthereto
operable for connecting said senders to said lines, 35 ing light load calling periods on each occasion
after lswitching connection is completed and' no
means responsive. to acall over a linev foroperat
other switching connection is in progress of com
ing a finder, the lines of each group preferring
pletion and a control mechanism automatically
said iinders in a particular order, mechanismrfor
operated by switching operations in said oiilce
normally advancing the order of preference se
for. determining when the order of preference for
quentially as said iinders and senders are taken
trunk iinders and senders shall be normally ad
for use during busy load calling periods, an auxil
vanced and when it shall be arbitrarily advanced.
iary device for arbitrarily advancing saidorder
6. In an automatic switching telephone oflice,A
of preference during light load calling periodsand
groups of lines, a plurality of finders inV groups,
a control mechanism automatically operatedu by
periodic switching operations in said cnice for 45 means responsive to a call over-a line for operat
ing a iinder, the lines of each ñnder group pre
determining when the order „of preference for
ferring said ñnders in a particular order, mech
ñnders and senders shall be normally advanced
anism for. normally advancing the order of pref
and when it shallbe arbitrarily advanced. `
erence sequentially as the findersl are taken for
3. In an automatic switching telephonek office,
use during busy lead. calling. periods andan auX
switches, groups of lines, a plurality of senders,
iliary mechanism for arbitrarily advancing said
a plurality of iinders in groups each having one
order. of preference after each call when. one
of said senders-permanently connected thereto
finder. completes a telephone connection and is
operable for connecting said senders tosaid lines,
released before another call requires the use of
erating a finder, the lines of each group preferring
means responsive to a call over a line for4 op
7.. In an automaticswitching telephone office,
groups of lines, a plurality of iindersin groups,
said finders in a. particular order, mechanism for
normally4 advancing the order of preference se
quentially as said finders and senders are taken
for use during busy load calling periods, an auxil
means responsive to a call over a line for operat
ing a finder, the lines of each finder group pre
iary device for arbitrarily advancing said order 60 ferring said finders» in a particular orden. mecha
nism for normally advancing the order of prefer
of preference during light load calling periods on
ence sequentially as the iinders are taken for use
each occasion after a switching connection is
during busy load calling periods, an auxiliary
completed and no other switching connection is in
mechanism for arbitrarily advancing` said order
progress of completion and a control mechanism
automatically operated by periodic switching op 65 of preference after each call when one finder
completes a telephone connection and is- released
erations in said oiiice for determining when the
order ofI preference for finders and senders shall
before another call requires the use of a finder,
and a control mechanism automatically operat
be normally advanced and when it shall abitrarily
ed by periodic switching operations responsive to
be advanced.
each call for determining when the order of pref
4'. In an automatic switching telephone office, 70 erence for ñnders »shall be normally advanced
switches, groups of lines, a plurality of senders,
and when it shall be arbitrarily advanced.
a plurality of finders in groups each having one
0f said senders permanently connected thereto
operable for connecting said senders to said lines,
means responsive to a call over a line for oper
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