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Патент USA US2104971

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\ Jan. 11, 1938.
o. l. CARPENTER |-_-r AL
Filed Dec. 2. 1955
5 Sheets-Sheet l
Jan. 11, 1938.
Filed Dec. 2. 1935
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Jan. 11, 1938.
Filed Dec. 2. 1935
5 Sheets-Sheet 5
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Patented Jan. 11, 1938
Oliver Irving Carpenter and Benjamin Francis
Moss, Coventry, England, assignors to The
General Electricl Company Limited, Coventry,
Application December 2, 1935, Serial No. 52,532
In Great Britain December 19, 1934
7 Claims. (Cl. 179-27)
The present invention relates to telephone sys
a tone to the said line such as a howler. Discon
tems and is more particularly concerned with ar
nection of the operator’s ’circuit from the junc
rangements for detecting faults occurring in au
tomatic or semi-automatic exchanges. It has
5. for its object the provision of means whereby an
operator at an attended exchange is informed
of the occurrence of a fault at an unattended ex
change connected to the one at which the opera
tor is situated.
In such unattended exchanges, a line fault has
hitherto been caused, after the lapse of a pre
determined period, to lock the aiîected line out
of use, and release any common exchange appa
Vratus which has been held operated by the fault.
This, in the case of an exchange diflicult of ac
cess, may mean that the particular subscriber’s
line on which the fault occurs is liable t0 be out
of commission for several days.
According to the invention therefore, means
20 are provided in an unattended automatic ex
change connected to an attended exchange,
whereby on the occurrence of a line or like fault
at the former exchange, an operator at the latter
exchange is informed, and may ascertain the
5 number of the faulty line. The operator may
also connect to the said faulty line, and apply
a tone such as a howler.
In an embodiment of the invention an unat
tended rural automatic exchange is connected by
30 one or more junctions to an attended or parent
exchange. If a line fault at the rural exchange
occurs, thefaulty line is isolated from the com
mon exchange apparatus after a predetermined
period, the said exchange apparatus being re
35 leased'. In addition, the faulty line seizes a group
of common apparatus connected via a junction to
the parent exchange, and the said common appa
ratus causes a signal to be sent over the junction
which informs the operator at the parent ex
40 change' that attention is required.
The operator connects her telephone circuit
to the junction and receives a characteristic tone.
She now dials a series of l’s until the character
, istic tone is removed. The total of l’s dialled, is
45 now the ñrst iigure of the number of the faulty
line. After a short time, the tone is replaced
on the line, and the operator dials a further-train
of l’s counting during the process. Removal of
the tone a second time gives the second figure
50 of the faulty line’s number. 'I'he process is re
peated as many times as there are digits in this
When the operator has ascertained the number
of the faulty line,..she may attempt to speakV to
the subscriber connected to it, or may connect
tion leaves the faulty line locked out in such a
manner that it cannot again seize the junction and
warn the operator until after the fault has been
In order that the nature of the invention may
be better understood, reference should` be made
to the accompanying drawings, Figure 1 of which
is a subscriber’s line circuit at an unattended
automatic exchange, and Figures 2 and 3 show
apparatus for conveyance to an attended ex
change of the number of a faulty line. One cir
cuit of the type shown in Figure 1 is provided for
each subscriber connected to the automatic ex 15'
change, one circuit according to Figure 2 is pro
vided for each 50 such subscribers, and the circuit
of Figure 3 is provided one for each unattended
exchange. As shown, a maximum of 200 sub
scribers can be accommodated, but this number 20
may be exceeded by obvious circuit additions and
Reverting to Figure l, the operation of this
circuit is of known character. When the sub
scriber lifts his receiver, a loop is formed from 25
earth on contact bl, over the subscriber’s line
wires, returning to battery via contacts b2, cl,
and the coil of relay A, which operates. Con
tact al removes marking potential derived from
contact b3 from the contact banks of the local 30
line finders, and contact a2 applies earth to a
start lead ST which initiates the hunting opera
tion of one or more line finders to find the calling
When a line finder arrives, an earth potential 35
is extended by it over lead P from the finder cir
cuit to operate relay B, and Contact b3 locks re
lay B operated to earth on lead P. Contact b4
operates relay C, contact c2 of which extends the
earth potential from lead P in the line finder 40
circuit to a corresponding lead inthe final se
lector multiple, thus marking engaged the call
ing subscriber’s line therein.
If the subscriber completes the call correctly,
subsequent release of the connection results in 45
release of relays B and C, but if for example, im
pulsing is not completed, a time delay circuit
(not shown) connected to the line finder circuit
comes into operation. After a predetermined pe
riod, earth is removed from the line finder lead 50
P, allowing relay B to release but holding relay
C over the loop. At the same time, an earth is>
applied, from the line finder circuit over lead 20
to operate the “start” relay ST in Figure 2 hav
ing access to the caller’s line. Relay ST operates
and at contact stl (not shown) disconnects the
brating its contact, supplying a characteristic
corresponding ST relay serving the other 50 sub- Y tone to the operator via sa! and lead I4.
scribers’ lines in the hundred group in which the
calling subscriber is connected. This contact is
connected in the second circuit in the position
shown by the sil contact in the dotted rectangle
in Figure 2 this contact belonging to the com
plementary ST relay. Contacts h3 and st3 in
the other dotted rectangle also belong to the sec
10 ond circuit. Contact st2 connects relays G and
H in series whereupon relay H does notroperate,
but relay G does. Contact st3 removes the earth
connection from the time delay circuit, thus pre
venting any other line finder circuit from extend
15 ing earth overv lead 20. Contact gl energizes the
switch magnet LF‘ which opens the interrupter
contacts Zf. Relay G releases, deenergizing the
magnet LF, which releases, moving all its wipers
one step forward.
This cycle continues, the relay and magnet in
terrupting one another’s circuits until wiper LF4
encounters earth applied to lead 5 via contacts
b5 and c3 from the line finder circuit over lead
M. This potential short-circuits relay G pre
25 venting its operation, and operates relay H
via contacts st2 and hl. Relay H at contact
hl locksV relay H operated via g3, bank LFS, lead
ä, c2, to earth at contact b3, at contact h2 op
erates relays HA and R in series via contact ml,
30 provided that no other HA relays are operated
at that time in series with R, at contact h3 pre
vents restoration of earth to the delay circuit on
release of relay ST, and at contact h4 applies
earth potential to the line finder circuit over
85 lead Zi, thereby freeing the line ñnder circuit
for use by other subscribers and permitting the
release of relay ST. -Relay HA at contact ha!
short-circuits the high resistance coil of relay
HA (which remains operated) this reduction in
40 resistance preventing the operation of any fur
ther I-IA relay in series with relay R, at contacts
ha2 and haii applies marking potentials to the
wipers LFE and LFS of the switch LF, at contact
had prepares to operate relay XA, at contact haä
45 prepares an alternative locking path for relay H,
at contact haâ applies a marking potential to
bank DS2, at contact hall reoperates relay G from
earth on contact h5, and at contacts has and
hall prepares a path for connecting the operator
50 at the attended exchange to the faulty line.
A delay period is now initiated before the op»
erator is informed that a fault has occurred.
This delay period is controlled by means of earth
pulses applied for example at 1 minute intervals
' to the lead connected to contact had.
The ñrst
of these pulses operates relay XA, and when the
pulse is removed, relay XB operates in series
over the path:--battery, wil of XA, coil of XB,
contacts :ral and r2 to earth. At the end of
60 the next period of l minute, a further earth pulse
applied via had holds relay XB operated via con
tact mbi, and short circuits relay XA Via contact
93172. This relay releases, as also does relay XB
at the end of the pulse.
Previous to this, however, contact rc3 operates
relay XC which locks operated via contact :co4
to r2. When earth potential is applied for a
third time to the hall lead, this potential is now
70 conducted via asbl and :tcl to lead l5 and thence
to repeating apparatus of known form which sig
nals the operator at the attended exchange, over
a pair of line wires, that a fault has occurred.
Contact :rc3 operates a buzzer relay BZ having
75 a self-interrupting contact bel, this relay, by vi
When the operator replies to the fault signal
as by plugging a cord circuit into the end of the
line over which the signal has been passed, relay
A is operated over lead il by the signalling ap
paratus at the unattended exchange. This ap
paratus is of the form of an impulse repeating
device, with holding facilities. Relay A at con
tact al operates relay B which thereupon at con 10
tact bl removes an earth potential from various
points in bank DSH, at contact b2 removes earth
potential from the remaining contacts of this
bank, at contact b3 supplies an alternative lock
ing path for relay R, and at contact b4 operates 15
relay RA.
The operator now proceeds to transmit a train
of single impulses as forÍ example by dialling a
succession of l’s by means of a dial or other im
pulse sending device, counting as she does so.
At the commencement of the first impulse, relay
A releases, its contact ai energizing relay C and
the switch magnet DS in series. Relay B is not
released, as it is slugged. At the end of the im
pulse relay A re-operates, and the switch mag 25
net DS moves the wipers 4DS 1-4 one step for
ward, though relay C does not release until
shortly afterwards. This relay C acts as a guard,
its contacts ci and c2 preventing premature op
eration of certain circuit members at the end of 30
each impulse.
The switch DS is stepped once each time the
operator dials an impulse until wiper DSZ reaches
the point in its bank marked by contact haíì. If
the faulty subscriber’s line is in the ñrst hun
dred group, this contact is the second in the
bank as shown, if the line is in the second hun
dred group, then the marking is extended over
lead il from another HA relay allocated to this
second group to the third contact in the bank.
When the marking is reached by wiper D52,
relay SZ operates and at contact sal removes tone
from the lead I4 connected to the remote op
erator, thus indicating from the number of irn
pulses dialled, the ñrst digit of the faulty line, 45
at contact ses connects earth potential to certain
of the connected contacts of bank DSI, thus step
ping the switch DS by self-interruption at its
own contacts ds to contact li, and at contact
324 holds relay SZ operated to contact bil.
To regain the tone in order to ascertain the
second number of the faulty line, the operator
dials a further single impulse. Relay A releases
and 1re-operates as previously described, operat
ing and releasing relay C and stepping the switch l..
DS one step further.
If the next digit of the faulty line is anything
other than l, no marking is found by wipermDSZ
and relay SZ releases when C operates, its YVccn
tact ssl re-applying tone to lead lâ. This is (ii)
heard by the operator, who continues to transmit
single impulses until a further marking in bank
DSE is encountered to operate relay SZ a second
time. This second marking in bank DSE is de
rived from the contacts and wiper of bank LF5, 65
the contacts of which bank are commoned or
connected together in groups of 10. The switch
LF, it will be appreciated, is a 50 point switch and
deals with the ñrst 50 subscribers in a hundreds
group; a similar switch connected to the leads 70
lil has access to the last 50 subscribers in the
group. As each group of 100 subscribers is
served by two switches such as LF, the connection
to banks LFE and LFë are multipled suitably to
the other switches, so that indications may beV 75
sent to the operator from any of the switches LF.
The second operation of relay SZ, in removing
tone from lead I4 informs the operator of the
number of the second digit of the faulty line. If
this digit had been l, then SZ would have re
mained operated and the tone would not have
been re-applied to lead I4, the operator’s in
structions being such that this would indicate a
second digit of l.
When the second digit has been transmitted,
the operator continues impulsing, relay SZ being
released as before, until wiper DS2 encounters
the marking made in the associated bank by
wiper LFS. The bank associated with this wiper
15 has'its contacts connected in groups of ten, thus
furnishing an indication of the third and last
digit of the> faulty line. At the end of the third
digit, operation of relay SZ followed by release
of relay C connects earth from cI via S23 to the
20 larger group of connected contacts of bank DSI,
the switch DS stepping its wipers by self-inter
ruption to the first contacts in their banks. Re
lay SZ remains operated via its contacts S24 to
trunk line extending from said exchange to an
operator’s board in a second exchange, means for
signalling the operator over said trunk line re
sponsive to a fault on a line in the first ex
change, and-means for enabling the operator to
ascertain the number of the faulty line, said last
means including an arrangement effective while
the operator sends trains of impulses over said
trunk line for notifying her when the total of
impulses in each train corresponds to a digit 10
of the number.
3. In a telephone system, a first exchange, a
trunk line extending from said exchange to an
operator’s board at a distant exchange, means
cont-rolled from a subscriber’s line in the ñrst ex
change for signalling the operator over said
trunk line, switching mechanism at said- first
exchange controllable by the operator over said
trunk line, and means including a device for
transmitting signals over said trunk line while 20
said switching mechanism is being operated for
enabling the operator to operate it in accord
ance with the number of said subscriber’s line.
4. In a telephone system, a first exchange, a
contact bI, so that the operator can now con
nect a speaking or testing circuit to leads I3
trunk line extending from said first exchange to
and I4 and thence via sel, S22, DS4, DS3, haS,
hall, LF2 and LFI to the faulty line, for the
a second exchange, means in the first exchange
responsive to a fault on a line in that exchange
purpose of speakingV or testing this line. When
these operations are completed and the plug with
drawn by the operator, relay A releases followed
by relays B, R, RA and XC. The latter relay at
its contact rc3 discontinues the operation of the
buzzer relay BZ and relay HA is released when
contact b3 opens its circuit. Relay HA in turn
releases relays H and G, and the apparatus is
ready for further transmission.
for signalling an operator in the second exchange
over said trunk line, a step by step switch con
trolled over said trunk line by the operator to 30
establish connection with the faulty line, and
signalling means in the ñrst exchange cooper
ating with said switch to notify the operator of
the number of the faulty line.
Should the fault on the line circuit be re
moved whilst the operator is connected to leads
I3 and I4, release of relay C (Figure l) cuts the
40 circuit of relay H at contact c2, and this relay
and relays HA and R all release. The equipment
is then restored to normal as though the oper
lator’s plug had been removed. If a number of
lines become faulty simultaneously, only one fault
45 can be signalled tothe operator at any one time,
as only one line finder such as LF can be set
into operation at any one time. Again, no fault
can be signalled twice to the operator, nor seize
a line ñnder circuit, since if the number of a
faulty line has been signalled the faulty line is
left with its C relay energized in series over the
line Wires via contacts cI, b2 and bl. This con
dition, however, is unable to apply a marking to
lead 5 since the line finder circuit from which
55 earth potential is derived over lead M has been
previously stepped offv the faulty circuit when
the switch LF reached the faulty line. The line
ñnder cannot again ñnd the faulty line until
after the fault has been removed, as relay A can
60 not be re-operated and consequently contacts al
and a2 cannot affect the line finder.
We claim:
l. In a telephone system, an unattended ex
change, a trunk line extending from said ex
65 change to an attended exchange, means in the
unattended exchange responsive to a fault on a
line in that exchange for transmitting a signal
over said trunk line to an operator in the at
tended exchange, and means controlled over said
70 trunk line by the operator for enabling such oper
ator to ascertain the number of the faulty line.
2. In a telephone system, a first exchange, a
5. In a telephone system, a first exchange, a 35
trunk line extending from a switch in the first
exchange to an operator’s board in a second
exchange, a finder in the first exchange respon
sive to an unstandard condition on a line to find
such line, means including said ñnder for mark 40
ing the bank of said switch in accordance with
the number of the line having the unstandard
condition, and signalling means in the first ex
change for enabling the operator to control said
switch in accordance with said marking, to there 45
by ascertain the number of the line having the
unstandard condition.
6. In a telephone system, a ñrst exchange, a
finder in said exchange responsive to an un
standard condition on a line to find such line, a 50
trunk line extending to an operator’s board in
a distant exchange, means responsive to the op
eration of said finder for signalling the operator
over said trunk line, and a switch controlled by
the operator over said trunk line to connect the 55
same with said finder and through the finder to
the line having the unstandard condition.
’7. In a telephone system, an exchange includ
ing a subscriber’s line, said line having a lock
out relay, means including said relay responsive 60
to a prolonged calling condition on said line to
lock out the line and terminate the calling con
dition in so far as it affects the switching equip
ment for extending the line, means responsive
to such lock out for signalling an operator in a 65
distant exchange, and means including switch
ing equipment in the first exchange controlled by
the operator for advising the operator of the
number of the locked out line.
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