US1923662A - Telephone system - Google Patents

Description

1933- A. E. CASWELL 1,923,662

TELEPHONE SYSTEM Filed Feb. 12, 1932 6 Sheets$heet l 1m HFThur Edward Gasman 1933- A. E. CASWELL 1,923,662

TELEPHONE SYSTEM Filed Feb. 12, 1932 6 Sheets-Sheet 2 15 LP 6P3 I 32 Fir Thur Edward Easmell Au 22, 1933. A. E. CASWELL TELEPHONE SYSTEM 6 Sheets-Sheet 3 Filed Feb. 12, 1932 IFEEZF HFfl'zur Edward Caswe ll 1933- A. E. CASWELL 1,923,662

TELEPHONE SYSTEM Filed Feb. 12, 1932 6 Sheets-Sheet 4 Irma? HFH-mr Eduard 555111511 Filed Feb. 12, 1932 6 Sheets-Sheet 5 Inner-11:11-

FlFZ'l-zux- Edward Gasman 1933. A, E. CASWELL 1,923,662

' TELEPHONE SYSTEM Filed Feb. 12, 1952 6 Sheets-Sheet 6 1m FlFn-lur Edward CasLuEll Fifi orrics TELEPH SNE SYSTEM 1r Edward Caswell, Liverpool, En land, as-

" r to Associated Telephone and Telegraph @hicago, llll, a Corporation Dela- 12, 1332, Serial l lo. 592,462, and in Greatliritain February 26, 1931 8 iUlairns. (Cl. HIS-17521) The present invention relates to telephone sysnumber of sub-areas or zones. The circuit artems and is more p ticularly concerned with rangements of the first code selectors in any what is known as routine apparatus, that exchange are such that the number of meter is to say apparatus arranged to reproduce auimpulses applied to the meter lead when a call tomatically the actual condition of use for each is being metered, or in other words the number of unit in turn of a large gr up of similar pieces times the calling subscribers meter isoperated of apparatus. The invention while not definitely for any one call, will be determined by the zone limited thereto is more specially applicable to to which the desired exchange belongs. The the testing of so-called first code selectors which routiner must therefore'be arranged to test this 10 may be broadly defined as first numerical multiple or zone metering function of the switches in a system employing register confirst code selectors.

trollers. In such a system a first code selector is According to the invention, therefore, means taken into use over an individual line switch or are provided in the routiner for testing the mulvia a line finder switch when a subscriber calls tiple metering function of the apparatus under 15 and thereupon temporarily associates itself with test.

a register controller adapted to respond to the The invention will be better understood from impulses dialed by the calling party. In due the following description of one method of can course the register controller sends out correrying it into effect which should be taken in sponding trains of impulses, the first series servconjunctl W the fi p yi g drawin s- 0 ing to operate the first code selector, and when These ShOW a 13011131118? adapted t0 test filSll code the connection has been completely set up the Se'ector switches of t e type disclosed in the register controller is released. Such a first code p fia O Of G & a F- T. 6 fi ed 8th selector is therefore considerably more compli- 511 6 93 e ia N 5'- d the general acated than a simple selector switch, and the ture of the tests applied is the same as described 25 routine tests must include some arrangements iIlPatelltNO-1,745,037gfa11l3ed 8 January 3 for testing also the apparatus for associating the to J. Ostline.

register controller with the connection. It is the Referring now to the drawings, Figs. 1 to 6, object of the invention to produce routine testthese ould be a a ed in nume cal Order in ing equipment which shall satisfactorily perform two rows under one another. They form a com- 30 all the functions outlined above, though it will p ots fi -Q Of @116 vesting Equipment 0f the ollbe understood that certain of the principles intillcf- T e Ope a of W ST 111 the access vowed can equally ll b applied to th t ti equipment during the movement of the switch of other kinds of apparatus. wipers to give access to th first of'the first code The testing equipment may conveniently be selectors (orasucceeding one whenatesthas been 35 divided into two parts, firstly the testing apparamade) Will operate relay P, Fig. 3, Of the routiner tus proper, and secondly the distributing switches over left-hand windin V Conductor 0 to by means of which the testing apparatus is asearth at armature s'i2, not shown. When relay sociated with the particular piece of apparatus it ST of the access equ releases at the end is desired to test. 01. he movement of the wipers the test start 40 The present invention utilizes a distributor eart W h rie fl y 2 Ofllhe rout-11161 switch scheme of a form well-known to those over its left-hand winding via the test start conskilled in the art, and it is therefore proposed ductor 11 (provided the test switch TS is normal) not to describe this part of the apparatus but over the following circuit: earth, test start cononly to make such reference thereto as may be ductor ll, armature H3; left-hand windings of found necessary in the more detailed description relay TH, first bank and wiper la of test switch of the routiner proper, or what may be termed the magnet interrupter springs tsdm, winding of testing equi ont of the routiner. Accordingly the t switch driving ma 'fi T551335 a y the scope of the accompainlinr drawings is convia the winding of r lay RA. Relay Til will lock fined to illustrations of the circuits employed in over rlght-han winding to the test start earth the testing e ui ment only. conductor 11, via its own operated armature tho In large telephone areas it is now usual to and armature N3, and at the same time armature charge subscriber for calls they make ap- 8152 w l isconnect relay P but the latter will proximately in proportion to the distances over hold dc to its until relay TH operates and which the calls are made in order to accomconnects the g t-hand winding of relay P to the plish this the tele hone area is divided into a private conductor 12 of the first code selector at 1 0 arinature me so that if the latter selector is eng ged relay P will be held on the busying earth. armature pl prevents the operation of relay TJ, Fig. 6, without which (at armature $78) the switch TS cannot step. If the lamp indicating key in the access equipment is operated, relay LR, Fig. 6, is operated to earth via lamp indicating key springs LKl and at armature Z74 connects earth to the selector busying lamp lLP, Fig. 1, which is wired to contact 1 of that bank of switch T3 with which the wiper 6a engages. The three minute delay set is started by the operation of armature t'izll, Fig. 4. The operation of this type of equipment is well-known and will result in firstly, an earth pulse being applied to the S pulse conductor 13 and secondly an earth pulse being applied after a definite interval of time to the Z pulse conductor 14. When the 2 pulse is applied relay TB will lock up and operate relay AL, Fig. 6, at armature 193. The operation of armature (114 will rin the alarm bell AB, Fig. 1, and light the rack pilot lamp RLP. Aruc e13 will bring in the main alarm, assumin that the main alarm cut-oil key MAK is normal.

If the first code selector under test becomes free before the delayed alarm is actuated relay P will release when the earth is removed from the private conductor 12 and at armature pl relay TJ will now be enabled to operate via armatures pfl and 13718 to earth, thereupon locking up via a mature tjS. At armature r' i9 the resistance YB, 3, relay PAE lower winding of relay BM connected in series to earth at resting armature bmZ. Relay PAE will operate in this circuit and operate its relief relay PE at armature peel, bt -elay BM cannot operate. At armature p53 a circuit for stepping the switch TS is prepared. he circuit is now in the conditionit would have in had the first code selector been found fl in the first instance.

Relay TH in operating at armature m4 has connected interrupted earth to relay IP, Fig. 4, and full earth via armature ipl to relay IQ so that relay 1? operates during the earth period, conveniently .75 second in duration, and relay IQ operates during the disconnect period which may be of the same duration, that is .75 of a second. Relay IQ however, will remain operated for a short period after the operation of relay IP due to the fact that its core is fitted with a slug and it is therefore slow to release, and during this "irne the magnet TEEDM of the switch TS will he ope "ased from earth, armatures aml, all, igl, p12, ps3, :53, first contact and wiper 4a of switch TS, winding of magnet TSDM, conductor 15 to battery via relay RA. When relay IQ releases the circuit of the magnet is broken at armature z'qi and the wipers of switch TS will therefore be stepped to the second position. At the second contact of the 5th bank on switch TS, relay AH will be operated from the earth at armature i712 at the second contact of the second bank (Fig. 3) of switch TS, the relay combination AN, AP and retard R is applied o the negative and positive conductors l6 and 17 respectively leading to the first code selector under test. These relays and relay L, not shown, of the first code selector, form a bridge in which if balance is maintained relay L will operate but relays AN and AP will not since they are so wired that their windings oppose with the local currents via armatures chi and 02713. A fault, such as a disconnection in the negative conductor 16 will cause relay AN to operate and a similar fault in the positive conductor 17 will cause relay AP to operate. If the conductors are reversed both relays will operate. A resistance earth or battery on the negative conductor 16 will operate relay AN and on the positive conductor relay AP this therefore constituting a test for contact with other lines. A short circuit on the conductors would have caused a false busy condition to exist by operating relay L in the first code selector and is in any case ested later. Due to the operation of armatures cpl and anl or @722 according to the relay or relays operated, relay AM, Fig. 2, will operate in series with the appropriate lamp of the lamp llLP, 12L]? and IBLP and at armature aml will disconnect the ci cuit of the mag net TSDM so that relay RA in series with it will not be operated. Armature m1 being opened, relay CT will not operate in order to open the circuit of relay TA at armature 0152 which is being connected to the S pulse conductor 13 by armature r7111. Thus the three minute delay set will come into operation resulting in the operation of relay TB which at armature "5223 will operate relay AL, and the latter at armature cal-5 will operate relay LR, Fig. 6, at armature 2T3 the low resistance upper winding of relay AM is connected across its lower winding so that the appropriate fault lamp will light.

If the loop test is passed correctly, that is, if neither relay AP nor AN operate, the test switch TS will be moved to the 3rd position when relay IQ releases the next time. Relay AH will release and the relay and retard combination previously mentioned are now replaced by a resistance YG of suitable value connected across the conductors 16 and 17 by wiper 2a and bank contact of the switch TS. No switch test is made in this position of TS and the latter will therefore step on to the 4th set of contacts. The operation of the L and B relays, not shown, of the first code selector will have caused the private conductor 12 to be earthed and relay PAE to be short-circuited, via armatures m9 and p3 so that relay PAE restores and releases relay RE. The circuit of the magnet TSDM is completed in the lth position of the wipers via resting contact of armature 1993 thus proving the guarding of the private conductor 12 by the first code selector, and if the latter has not taken place relays PAE and PE remain operated and the test switch TS is not stepped. After the delay period has expired the private uard lamp 3L1 is lit and the alarm given. If the guarding on conductor 12 is satisfactory the wipers or switch are stepped over contact 5 to contact 6 by relays IP and IQ. Meanwhile the first code selector been functioning normally and has caused its associated register con troller finder switch to hunt for and seize a disengaged register controller. When this occurs relay I; in the first code selector will operate and switch through the operating leads to the register controller thereby releasing relay I in the first code selector.

It should. be mentioned that for facilitating the will have no effect upon the functioning of th routiner under discussion.

' Returning now to the routiner it will be seen that when relay I of the first code selector re leases, earth will be connected to the I relay conductor 18 to operate relay DA via armature m which at armature cZal steps the magnet TSDM via interrupter springs tsdm, wiper 7a and bank contact. If a register controller is not seizec relay DA will not operate to step the switch TS so that after the expiration of the delay period the appropriate lamp ALP will be lit and the alarm given.

No impulses are sent into the register controller in this position of the routiner so that after a certain interval a so-called forced release condition will obtain in this latter switch and will result, as is well-known, in the release of relay K of the first code selector. Relay I of the same switch will therefore re-operate and release relay DA of the routiner by disconnecting earth from the I relay conductor 18. The test switch TS is then driven to the 8th position via resting contacts of armature deli and interrupter springs tsdm, wiper 7a and bank contact. Failure of the register controller to originate the forced release condition will maintain relay DA operated, the register controller forced release lamp LP will be lit and the alarm given. Assuming that the fault condition does not exist the wipers of the switch TS will now be stepped from the 8th to the th position by vthe'interaction of the pulsing relays IE and IQ in order to provide a period for the release of the first code selector which will take place when the loop completed by wiper 2a and bank contact is broken in the 8th and 9th positions of the switch TS. With the latter switch in position 10 a circuit for relay L of the first code selector will be completed via a resistance YE which is of the correct resistance for testing the sensitivity of operation of the L relay. This resistance is connected across the conductors 16 and 17 via the wiper 2a and bank contact and armature sal which is normally short-circuiting the so-called loop pulse springs LPS. The private conductor 12 will be again earthed and relays PAE and PE released. At armature pe2 a circuit for the magnet TSDM is completed via bank contact and wiper 4a of the test switch so that upon the first release of relay IQ, the test switch TS is stepped to the 11th position. The private guard lamp BLP will again light should a fault occur. No test takes place in the 11th position so that switch TS will eventually step to the 12th position. When a disengaged register controller has been seized the switch TS will step to the 13th position in response to the operation of relay DA in a manner similar to that already described. Relay SS will now operate via the 13th bank contact and Wiper 5a of switch TS, armature thil to earth, and at armature s32 connects relay CC, rig. 5, to the socalled magnet pulse springs MPS which vibrate at the same speed, conveniently 10 pulses per second, but in phase opposition tothe loop pulse springs LPS. the same time armature 8S3 comiects earth to the side of the upper winding of relay CC via armature 521. If this occurs when the magnet pulse springs MPS are closed relay CC will be short-circuited and will therefore only operate at the conclusion of the earth pulse, that is, when springs MPS open. Relay CC at armature ccl switches the magnet pulse springs MPS to the so-oalled sender switch magnet SDM so that the wipers of the sender switch SS will be rotated under the control of the mag-- net impulse springs MPS.

'At this time the wipers 10 to of the zone select switch ZS, Figs. 2 and 5, will be in their 6th position provided that none of the so-called zone select keys ZSK2 to ZSK6 have been operated. The movement of the wipers of ZS takes place on the initial operation of relay TH via armature th? and wiper 2b and first bank contact of the sender switch SS, conductor 29, first five bank contacts and wiper 2c of switch ZS, interrupter springsesdm, to winding of magnet ZSDM to battery over relay RA. A contact of that bank of the sender switch SS associated with wiper 3b has therefore been earthed from earth at armature th2, armature shl, wiper 4c of switch ZS, 6th bank contact which is cross connected to a particular digit lead and thus to the bank contact of the switch SS. As the sender switch is being pulsed relay SA is operated at the second contact of the bank with which'wiper 2b engages and at armature sal removes the shortcircuit from the loop impulse springs LPS. The L relay of the first code selector is therefore impulsed until the wiper 3b of the. switch SS reaches the contact marked by earth in a manner outlined above. Relay SZ will then operate and lockat armature sea via armature m2, at armature se2 the loop pulse springs LPS will be again short-circuited, atarmature $23 a circuit is completed to enable the sender switch driving magnet SDM to drive its wipers to the 13th contact, while armature 321 allows relay CC to release. When the switch SS reaches its 13th position the earth from armature m7 is connected via wiper 2b and 13th bank contact, conductor 26, 13th bank contact and wiper 7a of switch TS, interrupter springs tsclm to the winding of the magnet TSDM so that the wipers will be driven to the 14th position, whereupon relay SI-I operates via the bank contact and wiper 5a of switch TS and armature m2 and at armature sh2 holds relay SS. At armature sh3 a high resistance YF is connected across the negative and positive conductors 16 and 17 to simulate the minimum leak resistance allowed in practice on any line and to test the impulsing of the L relay of the first code selector under these conditions. At armaover from wiper 40 to 30 of switch ZS and since the 6th bank contact upon which wiper 30 will I troll'er is such as to route the connection to a,

spare level reserved in a group or code selector for the routiner test line. After the second digit has been sent the sender switch SS rotates to its 25th contact and the test switch TS is steppped as before to its 15th position.

If due to any fault,'connection is not made to the test line, relay TT, Fig. 2, will be unable to operate and the test line seized lamp 6LP will remain alight and alarm will be given. If the test line is found, however, and the first code selector connections are in order, relay TT will opcrate over conductors 34 and 35 in series with relays D and I of the first code selector, whereupon the I relay will operate but not the D relay. In operating, relay I will remove earth from the I relay conductor 18 and allow relay DA of the routiner to restore. At armature ttl the pulsing circuit to the magnet TSDM is closed via the bank contact and wiper 4a, resulting in the wipers of the switch TS being driven to the 16th position whereupon relay BR, Fig. 4, will operate via the 16th bank contact and wiper 5a of switch TS and at armature brl connect negative battery to the positive test line conductor 35 via the lower winding of relay TT and armature dd2. This is to simulate either (a) the battery period of the well-known busy flash used for informing a calling manual operator of a busy condition or (b) the well-known operator holdccndition which is set up by an operator who wishes to hold a connection after the calling subscriber has restored.

As a result of the negative battery being connected in the manner described no current will now flow in the circuit including relays D and I of the first code selector and relay TT in the T routiner. In consequence relays TT and I restore so that relay DA will operate, and at armature da3 prepare the pulsing circuit of the magnet TSDM via bank contact and wiper 4a which will operate upon the next operation of armature ip2 and rotate the wipers of the switch TS to the 17th position when relay IQ restores.

It is apparent that in the event of the register controller failing to reach the test line it would be possible for the test switch to be stepped froin the th to the 16th position by the ction of an ordinary subscriber erroneously seizing the the test line. In this case the test switch would not pass the 16th contact (so keeping lamp 6L1 alight) since the operators hold feature would not be siin ilated on the line (other than the test line) reached by the register controller. In the event of the test switch successfully passing contact 16 relay DD operates via the 17th contact and wiper 5a of the switch TS and at armatures ddl and cZdZ reverses battery and earth which are connected via the windings of relay TT to the test line thereby operating the polarised relay 1) of the first code selector in order to prepare the metering circuit in the latter switch. The code which has been sent out from the register controller in the normal case will have operated the first code selector to a level which will result in'one impulse being applied to the meter lead, that is to say, as for a unit fee area. Relay BM, Fig. 3, will operate over its lower winding in series with relay PAE when booster battery is applied to the private conductor 12 by the first code selector this con stituting the meter impulse, and will lock over both its windings in series when the short-circuiting earth is removed from its upper winding by the operation of armature bm2. The

armature 237212 serves to prepare the circuit of the magnet TSDM via conductor and bank contact and wiper "1c in order to step the be again short-circuited, so that the circuit of the magnet ZSDM will be broken at armature bml and the wipers of the switch ZS will therefore be stepped to the 7th position. Relay MT willnow operate via the 7th bank contact and wiper 4c of switch ZS, armature shl, armature M2 to earth, and at armature mil prepares a circuit for the magnet TSDM via bank contact and wiper 7a and interrupter springs tsdm in order to step the wipers of the switch TS to the 19th position.

Any failure would result in the metering pulse not being received or relay BM not operating. This would leave the test switch in the 17th position, light the meter fail test lamp 7L]? and after a delay period give the alarm. The test switch is allowed to pass through its 19th and 20th positions under the control of the pulsing relays IP and IQ.

Should further metering occur, the magnet ZSDM will operate from armature bml, and step its wipers to the 8th position thereby releasing relay MT. If this occurs during the pulsing of the test switch TS over the two preceding contacts, the te t switch will remain in the 21st position, light the incorrect metering lamp BL? and give the alarm. If no over-metering occurs, relay WET will remain operated in order to step the test switch wipers from the 21st to 22nd position through the medium of armature mtl.

In this position of the test switch TS relay RT, Fig. l, will be operated via the 22nd bank contact and wiper 5c of the test switch, while the conductors l6 and l? are short-circuited via Wiper 2a and bank contact or" the switch TS and wiper 2d and first bank contact of the so-caile release timing switch RTS. Arma tnre r54 connects eartli from armature pcl to pulse springs PPS, which may be arranged to vibrate at conveniently 20 pulses per second, and which short-circuit relay RG, Fig. 6, during their make period. Relay RC4 operates on the short-circuit being removed and at ar mature "r92 switches the pulse springs PPS to the magnet RTDM of the pulse timing switch RTS. On the first step of the wipers of the latter switch the loop across the negative and positive conductors 16 and 1'? is broken by the movement of wiper 2c; the first bank contact and the first code selector thereupon commences to release. This will result in earth being removed from the private conductor 12 so that relay PAE will operate to b followed by the relief relay PE which at armature pel breaks the circuit of relay RG the magnet RTDM thus stopping rotation of the wipers of the switch RTS. Relay HG in releasing connects earth to wiper 4d of switch RTS and if the time of release of the first code selector has been within the correct limits the test switch is stepped to the 23rd position by this earth via wiper id and bank contact of switch HTS, conductor 28, 22nd bank contact and wiper 7a of the switch TS, interrupter springs tsdm and winding of driving magnet TSDM to battery via winding of relay RA, Fig. 4. If, however, the time of release had been either too fast or too slow the appropriate lamp of the two lamps FELP and SRLP (fast release lamp and slow release lamp) would have been lit and relay AM 0perated. Earth from armature Hi2 will now be connected via the wiper 5a and 23rd bank contact of switch TS to conductor 37 to operate relay TE, not shown, in the access equipment so that the access switch will be eventually stepped to find the next switch to be routined. Earth will also be removed from the test start conductor 11 by the operation of relay RF.

The routiner rotary switches return to their normal position and all operated relays release.

It will be advisable occasionally to put a more complete test on the first code selectors in order to test the metering for calls to difierent zones. This will not be included in the ordinary routining but at various intervals metering to a particular zone may be tested as follows:

In order to make the test it is only necessary to o erate the appropriate zone select key 2257c, 3237:, ic sic, 5zs7c or desk. The correct routing of the call will already have been ensured by the cross connections from those banks of the zone selecting switch ZS which are engaged by wipers 3c and lo to that bank of sender switch which is engaged by wiper 3b. The cross connections cause the sender switch SS to send such a numher into the register controller as will be translated by the latter switch in such a manner as to effect the routing of the call to the required office in the chosen zone. If an automatic exchange is available in the required zone the call will be routed to special equipment on a spare level or associated with a spare number. If no automatic exchange is available in the required zone the call will be routed over the ordinary junctions to a manual exchange and a special tone will be given to the manual operator when she replies by inserting the answering plug of a cord circuit into the answering jack. Having ascentained by the reception of the tone, that the call is from a routiner, the operator will insert the calling plug of the cord circuit into a special routiner jack having its tip and ring connected together to simulate for the routiner what may be termed a called subscriber replies condition.

In order to describe in greater detail tests applied by the routiner in cases of multiple or zone metering, it will be advisable to take a particular example, for instance, assume it is desired to routine zone 3. For this purpose the zone select key 3257c must be thrown. When the routiner start wire is earthed relay TH will operate and earth from armature m7 will e connected to the contacts of that bank of switch ZS with which wiper 20 engages, via springs of the non-operated zone select keys 228702, eslcZ, 52sk2 and 6cslc2. The fourth contact on the bank will be disconnected by the operation of springs 3ZSK2 and the wiper of the switch ZS will therefore come to rest in the fourth position. Relay ZS will also be operated via make contacts 3ZSK1 of the operated key and at armature cs1 applies the special tone already mentioned which may conveniently take the form of number unobtainable tone to conductor 16 via condenser QB. Armatures cs2 and 283 connect contacts 15 and 16 of the 4th bank of the switch TS to the pulsing circuit formed by armatures i132 and iql so that the test switch TS will pass over the test line seized contacts. In addition armature cs4 earths the private conductor 36 of the test line to busy the line against subscribers or other false calls.

The test will now proceed as in ordinary routing. The test switch TS will be rotated through the 15th and 15th positions without making any tests. In the 17th position of the test switch TS, relay D in the first code selector operates when the called subscriber replies condition is set up and the metering pulses are commenced. If the operator does not reply or if metering is not started relay BM will not operate and the test switch TS will not move from the 17th position. If, however, the operator replies and metering is commenced relay BM will operate and at armature hmZ the test switch magnet TSDM is operated via bank contact and wiper 7a of the test switch TS, and interrupter springs tsdm the wipers being, therefore, rotated to the 18th position. Armature bml completes a circuit for the ZS switch magnet ZSDM via the bank contact and wiper 3a of the test switch and on the termination of the metering pulse relay BM restores so that the magnet ZSDl/l steps the wipers of the I 19th position after which'the pulse relays IP and IQ will step the test switch to the 21st position. If excess metering has taken place during this stepping, relay MT will have released, but if not the latter relay will still be operated and the test switch TS will be stepped to contact 22.

When routining incoming first code selectors,

that is, those which terminate two wire junctions,

relay DS, Fig. 6, will be operated in a manner similar to that described in relation to relay PE in my application Serial No. 534,829, filed 4th May 1931. No metering pulses are sent out from these switches but instead the current is reversed in the calling line to operate metering equipment on the other end or" the junction. The routiner must therefore be capable of utilizing this battery reversal condition in order to test the metering function of the first code selector and this is effected by relay 1) in the routiner which is connected across the conductors l6 and 17 when the test switch is in its 17th, 18th, 19th, 20th and 21st positions.

Irrespective of which zone is being routined or which zone select key is off normal the first five contacts in the second bank of the switch ZS will be earthed via operated armatures (Z33, 4, 5, 6, and 7, first contact and wiper 2b of the sender switch SS, operated armature th'? to earthv so that the ZS wipers will be rotated to the 6th position when relay TH operates. When relay D operates the switch ZS moves to the 7th position due to the circuit of the magnet ZSDll/l being com- 1" to the contacts '7 to 12 inclusive of the ith banlz of the switch TS so that the wipers of the latter switch will be quickly rotated over these contacts after which testing will proceed normally.

It will have been seen that false metering such as insuflicient or over metering is tested during the metering testing period, but it should be pointed out that if, due to a fault, a metering pulse is given at any other time than that during which metering should normally take place,

relay FM, Fig. '1, will operate via the operated The speed of testing first code selectors position. There is now no armature lam-l wip 3a and contacts of the switch TS and will loos. via armature m3 to earth at armature 3. 2.2. Armature fml operates relay AI.- in order to give an i. nediate and stop the test switch, ile armature fm2 lights the false mete i g lamp 1414?. The particular lamp in the group of I" hit lamps, 1LT? to 10LP, connected to the 6th r of switch TS which will light when relay R operates will also serve to give an indie o period of test at which the false metcrin Should the earth on be removed at any tr er than when it is removed by the routi PAE and PE will operate and result in the operation of relay EP, Fig. 1, via armatures m2, bml and pea, wiper 8a and bank contact of switch. winding of relay EP which thereupon lcc'ns via armatures c132 and ms to earth. A mature cpl operates relay AL in order to originate e while arnature e103 lights the no car. on P wire lamp 15;?

Should a routiner switch magnet become energized for an excessive period relay EA will remain operated in series with the magnet and at armature m2 initiate the so-called 9 seconds delay set and an alarm will be given.

What I claim is: r

1. Testing apparatus for testing a selector switch of the type used in automatic telephone systems, which switczis arranged to transmit metering impulses in accordance with the position it is set in, said apparatus including means for transmitting impues to set said switch in a position to transmit metering impulses, and means in said apparatus operated by said metering impulses to test for the correct transmission of said metering impulse 2. Testing apparatus for testing a selector switch of the type used in automatic telephone systems, which switch is arranged to transmit metering impulses in accordance with the position it is set in, the different positions of said switch corresponding to the different zones in the telephone system, said apparatus including means for transmitting impulses to set said switch ate conductor 12 in different positions corresponding to the difi'erent zones to transmit metering impulses the number of which varies dependent upon the position the switch is set in, means in said apparatus modified in accordance with the number of impulses transmitted to set said switch in a certain position, and said modified means thereafter operated in response to said metering impulses for continuing the test of said switch only in case the number of metering impulses sent back by said switch corresponds to the zone represented by the impulses transmitted to set said switch.

3. Testing apparatus for testing a selector switch of the type used in automatic telephone systems, which switch is arranged to transmit metering impulses in accordance with the position it is set in, the different positions of said switch corresponding to the different zones in the telephone system, said apparatus including means for transmitting impul es to set said switch in different positions corresponding to the difierent zones to transmit metering impulses the number of which varies dependent upon the position the switch is set in, means in said apparatus modified in accordance with the number of impulses transmitted to set said switch in a certain position, said modified means thereafter operated in response to said metering impulses for continuing the test of said switch only in case the number of metering impulses sent back by said switch corresponds to the zone represented by the impulses transmitted to set said switch, an alarm relay in said apparatus, and means for operating said alarm relay in case the 1 umber or" meteringiinpulses fail to cor espond to the zone represented by the impu transmitted to set said selector switch.

4. Testing apparatus for esting a selector switch of the type used in automatic telephone systems, means in said apparatus for transmitting impulses to said selector switch, meter impulse responding switch and a sender switch in said apparatus, means jointly controlled by said meter responding switch and said sender switch for determining the number of impulses transmitted to said selector switch, said selector switch operated to a certain position in accordance with the number of impulses transn 'tted thereto and arranged to transmit metering impulses back to said apparatus in accordance V. 'th the position it is set in, and means in said apparatus operated in response to said metering impulses for operating said meter responding switch in accordance with the number of metering impulses transmitted to ch ck the metering operation of said selector switch.

5. Testing apparatus for testing a selector switch of the type used in automatic telephone systems, which selector switch is arranged to transmit metering impulses in accordance with 1 the position it is set in, the different positions of said selector switch corresponding to the different zones in the telephone system, a meter impulse responding switch, a sender switch having a wiper and bank contacts accessible thereto, means in 1 said apparatus for operating said meter responding switch to mark one of the bank contacts of the sender switch in accordance with a certain zone, means in said apparatus for transmitting 1 impulses to said selector switch and for simul taneously operating the wiper of said sender switch one step for each impulse transmitted, means for stopping further transmission of said impulses in response to said wiper engaging said marked bank contact, said selector in response to 1 said impulses being set in a certain zone position to transmit back to said apparatus a certain number of metering impulses, and impulse responding means in said apparatus operated in response to said metering impulses for further operating said meter respondingiswitch in accordance with the number of metering impulses transmitted to check the metering operation of said selector switch.

6. Testing apparatus for testing a selector 1 switch of the type used in automatic telephone systems, which selector switch is arranged to transmit metering impulses in accordance with the position it is set in, the different positions of 1 said selector switch corresponding to the different zones in the telephone system, a sender switch and meter switch in said apparatus, means for transmitting impulses to said selector switch, means for operating said meter switch to hunt for and stop said meter switch in a position cor-- responding to the zone position the selector switch is to be operated to, means jointly controlled by said meter switch in the position it is stopped in and said sender switch for determining the num-,

ber of impulses transmitted. to said selector meter checking relay in said apparatus, means in said apparatus operated in response to said metering impulses for operating said meter switch to a diiierent position for each meter impulse transmitted, and a circuit including a predetermined position in said meter switch completed for operating said relay in response to transmission of the correct number of metering impulses.

'7. Testing apparatus for testing a selector switch of the type used in automatic telephone systems, which selector switch is arranged to transmit metering impulses in accordance with the position it is set in, the difierent positions of said selector switch corresponding to the diiierent zones in the telephone system, a sender switch and a meter switch in said apparatus, a plurality of keys in said apparatus, each. key corresponding to a particular zone, means for operating said meter switch to hunt for and stop in a position corresponding to an operated one of said zone keys, means jointly controlled by said meter switch in the position it is stopped in and said sender switch for determining the position to which said selector switch is to be set in, said selector switch being operated to the position corresponding to the zone key operated to transmit metering impulses back to said apparatus, and impulse responding means in said apparatus operated in response to said metering impulses for further operating said meter switch to check the metering operation of said selector switch.

8. Testing apparatus for testing a selector switch of the type used in telephone systems, which switch is arranged to be set in different positions corresponding to different zones and to transmit metering impulses in accordance with the zone position it is set in, means in said apparatus operated by said metering impulses to test for the correct transmission of said metering impulses, a tone source for generating a distinctive tone, and means in said apparatus for connecting said tone source to said selector in case said selector is operated to a position extending the connection to a manual exchange.

ARTHUR EDl/VARD CASWELL.

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