US1854456A - Testing arrangement for automatic or semiautomatic telephone systems - Google Patents

Description

April 19, 1932.4 DEAKlN AL 1,854,456

TESTING ARRANGEMENT FOR AUTOMATIC OR SEMIAUTOMATIC TELEPHONE SYSTEMS Filed May 15, 1950 s Sheets-Sheet 1 I V O G.DEHK\N- N ENT Rs L. POLIN KOWSKY, oacznssn, EDOURD FRUM fiummls'rnmolz ATTORNEY April 19, 1932. G. DEAKIN ET AL 1,854,456

TESTING ARRANGEMENT FOR AUTQMATIC OR SEMIAUTOMATIC TELEPHONE SYSTEMS Filed May 15, 1930' a Sheets-Sheet 2 IHVENTORS G. DEA KIN Po UN KOWSKY, nscensen Eoouan FRu'M ADMINISTRATOR 'BYzai a.

ATTORNEY April 19, 1932. G. DEAKIN ET AL 1,854,456

TESTING ARRANGEMENT FOR AUTOMATIC 0R SEMIAUTOMATIC TELEPHONE SYSTEMS Filed May 15, 1930 3 Sheets-Sheet 3 FIG. 3

mvawmszs G.DEAKIN L,POL\H 0WSKY nzcenssn ioounn'o FRUM, ADMINISTRATOR ATTORNEY Patented Apr. 19, 1932 UNITED STATES PATENT OFFICE- GERALD DEAKIN, OF NEW YORK, N. Y., AND LIIPA POLINKOWSKY', DECEASED, LATE OF PARIS, FRANCE, BY EDOUARD FR-UM, ADMINISTRATOR, 0F PARIS, FRANCE, AS-

SIGNORS T0 INTERNATIONAL. STANDARD YORK, n. Y.

ELECTRIC CORPORATION, OF NEW TESTING ARRANGEMENT FOR AUTOMATIG 0R SEMIAUTOMATIG'TELEPHONE SYSTEMS Application filed May 13, 1930, Serial No. 452,085, andin Great Britain May 14, 1929.

The present invention relates to automatic or semi-automatic telephone systems and is more particularly concerned with arrangements for effecting routine tests of apparatus used therein. Such tests consist in periodically operating such apparatus in the same way as would occur if it were being used in the setting up of ordinary connections.

An object of the invention is the provision of a simple and efficient arrangement for testing the switching apparatus in an exchange of the kind in which the conversation selector switches are operated under the controlof control circuits each common to a plurality of conversation switches but individual to a particular switching stage.

According to'one feature of the invention in an exchange of this kind, a testing arrangement is provided which is adapted to -be associated automatically in turn with each of a plurality of conversation switches and to perform automatically a series of operations similar to those operations which would occur in an ordinary connection where- 5 by the operation of each of said conversation switches in conjunction with an associated control circuit is tested;

In accordance with another feature in an exchange of this type means is provided whereby a testing circuit is adapted to be associated in succession with conversation switches having associated therewith different control circuits, whereby a rapid test of I the control circuits may be affected.

According to a further feature in an exchange of the above kind, test circuits are provided for testing the apparatus at each numerical switching stage, such test circuits being provided with means for taking into use in turn each one of a number of the switches used in establishing a connection and for automatically extending a connection thereover toa predetermined test line.

A still further feature consists in the provision of a testing circuit for automatically testing in turn the operation of a plurality of'link circuits each comprising a backwardly hunting finder switch and a group selector switch, in which means is provided for controlling theadvance of thefinder switch of a link to be tested to a test line which tera connection to be extended over the group selector switch of said. link circuit to a further test line extending back to said testing circuit.

These features will be more fully appreciated from the following description of, one method of carrying the invention into effect which is given by way of example and should be studied in conjunction with the accompanying drawings. It will be understood, however, that the invention is not limited to the particular arrangement shown and that various other circuit, arrangements could be readily devised by those skilled in the art without departing from the scope of the appended claims.

In the following description the invention is described as applied to a system of the kind fully described in our co-pending U. S, application No. 37 0,67 3, which used the principle of revertive control of single-motion power driven switches controlled by common control circuits.

It has not been considered necessary. to illustrate or describe in detail the operation of the switching apparatus to be tested as this isidentical with that described in the specification previously referred to.

Referring now to the accompanying drawings.

Figure 1 shows schematically the layout of a system of the kind referred to and enclosed Within the dotted line rectangles, three testing circuits for testing the switching apparatus at the first, second and third switching stages respectively.

Figure 2 shows the testing circuit for testing the second line finder and first group selector link circuits.

Figure 3 shows the testing circuit for testing the second group selectors and their associated control circuits.

Figure 4 shows the testing circuit for testing the final selectors and their associated control circuits.

Referring first to Figure 1, a brief description will be given of the switching apparatus involved in an ordinary call between a calling subscriber S and a wanted subscriber S1, followed by a general explanation of the manner in which the testing circuits are used to make the required routine tests.

A calling subscriber S is extended over first and second backwardly-hunting line finders lLF, QLF to a first group selector finder lGF having associated therewith an idle control circuit lCF. Immediately thereafter the link circuit comprising the second line finder QLF and the group selector lG'F becomes attached to an idle register controller RC over a finder PR whereupon dialling tone is sent to the calling party. Four digits are non-dialled into the register controller RC which thereafter controls the extension of the call of the first group selector lGF, a-second group selector EGF and a final selector FF, these selectors bein operated under the control of common control circuits lCF, QCF, FCF which send revertive impulses to the register-controller RC.

The testing circuit T1 is arranged to test 100 link circuits such as 2LF-1GF. A test line TL extending from the testing circuit T1 is multipled in the banks of each line finder QLF of this group of 100 links and is arranged to be marked as calling in the bank of any one of these finders over a brush of a 100-point switch TF associated with the testing circuit Tl. When the test is commenced, the test line TL is marked as calling to the finder QLF of a link on which a testis to be made, and the finder switches of the group to which the finder to be tested belongs are advanced until this particular finder engages the test line TL. WVhen an idle register-controller RC has become attached to the link under test, an impulse sending switch associated with the testing circuit Tl automatically sends into the register controller RC four digits necessary for extending the call over the first group selector IGF, a second group selector QGF and a final selector FF to a test line lTL which terminates in the final selectors and extends back to the'testing circuit T1. By throwing a special key the impulse sending switch in the test circuit may alternatively be caused to stud two digits to the register to direct the connection to a special service group in the second selector QGF from which a test line STL extends to the test circuit T1. In either case if the apparatus has functioned correctly a relay is operated in the test circuit T1 and the switch TF is advanced to the next second line finder and the test is repeated.

The testing circuit T2 is arranged to test 100 second group selectors and their associated control circuits and has associated with it a 100-point switch TGF which has access to these group selectors over three wires in exactly the same manner as a preceding first group selector. A switch is provided in the testing circuit which simulates the action of a register controller in controlling the extensiqn of a connection to a test line 2TL which terminates in the final selectors and extends back to the control circuit. If the apparatus has functioned correctly the switch TGF is advanced to the next group selector and the test repeated. Provision is made whereby the switch TGF may be successively advanced to group selectors served by different control circuits in order that a rapid test may be made of the control circuits.

The testing circuit T3 is similar to the testing circuit T2 with the exception that it controls two selective operations to extend connection over a final selector picked out by the switch TFF to a third test line 3TL.

In each testing circuit means is provided for advancing the switches TF, TGF, TFF under manual control to test predetermined switches.

A detailed description of the operation of the testing circuit T1 will now be given with reference to Figure 2.

When the start key AK is depressed relay T1" is energized over a circuit, ground, AK l, brush and contact of bank d, of switch TF, A1 2. A circuit AK&5, Mr1, STE, F76 is also closed for relay Br which at contacts B1 2 holds open the circuit of relay L1". Relay T1- opens the circuit of the power magnet PF at contacts Trl, lights a lamp TL to indicate that the test finder TF is arrested on a terminal set, and at contacts TrfZ closes a circuit for relay Cr which extends from ground at springs 2 of key DK, GT3, AK2, Tr2, AKl, CW1, winding of C7" to battery. Relay Ur locks up over its make-before break springs C1"l2, DKl, Mrl, AK54=, at contacts CM closes a circuit for relay A1", which locks to springs AK45 and at contacts GT6 closes a point in the 6 Wire of the test line TL.

A check is now made to determine whether any line finders of the group to which the finder to be tested belongs are rotating. This is effected as follows: Relay C?" at contacts Cr7connects relay 01' via contacts F12 and the brush 6 of the test finder TF and strapped contacts of the arc to the starting circuit of the finder group, and at contacts C1 5 closes a circuit for a slow-acting relay S1" from ground at contacts @1 1. If there is a call in the finder group the start relay C87" is energized and the quick acting relay O1" energizes over the front contacts of relay CS7 and opens the circuit of relay Sr before this relay has time to operate. When relay C87 falls off. however relay O1 relapses and completes the circuit for relay S? which locks over Srl, Mrl, AK54 and opens the circuit for relay Br. Relay In" is now energized over the following circuit,-battery winding of relay Lr, Ere, B122, GT6, contact and brush 6 of impulse sending switch IF, springs 4 of 'I which transmits slow impulses.

key ElQ Rrl, springs 2 of jack MJ, Erl to ground. Relay L1 at contacts L1 1 connects a test potential to the test terminal of the finder to be tested via brush 6 and terminal of the test finder TF and at contacts LrQ closes via brush 0 the circuit of the starting relay Her of the group of finders including the finder to be tested. Relay Her closes the circuit for the power magnet PL of the finder to be tested and other finders of the group and when this finder engages the test terminal set, relay E1? is energized over the 0 wire at contacts Erl opens the circuit of relay L1 and at contacts ErQ energizes relay Fr.

The relapse of relay L1 opens the start circuit and removes the test potential from the brush a of the test finder TF. Relay Fr initiates a test for checking whether a register 7 controller has become attached to the finder under test. Relay F r at contacts F14 connects the winding of relay B1" to the starting circuit of the group of register controllers serving the line finder link under test. If a register controller has not been attached relay Br energizes over the front contacts of the start relay Ar and holds open the driving circuit of the impulse sending switch 1F until the relays Ar releases. With relay Fr energized and relay Br de-energized, the driving magnet IP of the impulse switch is energized over the following circuitbattery, magnet 1P, springs 1 of ack MJ, Irl, Grl, Brl, F1 1, Nrl, AKti-i to ground.

The switch IF is equipped with five brushes. The brush 0 or 6 (according to the operated or non-operated condition of a key EK) is connected via contacts Rrl, ii /L12, to the a wire of the test line TL and the contacts .engaged by these brushes are strapped together and connected to the 6 wire. The contacts engaged by the brush 0 are so spaced that the switch in rotating transmits fast impulses over the loop a Z) whilst the contacts engaged by the brush 6 are so spaced that in rotating slow impulses are transmitted over the loop. The contact rows wiped over by brushes a and 6 determine the number of impulses transmitted by'the switch, the row wiped over by brush a being correspondingly spaced to the row engaged by brush 0 which transmits fast impulses, and the row wiped over by the brush 6 being correspondingly spaced to the row engaged by the brush 6 By means of the strapping terminals XY any pair of contacts in the rows a, b may be connected to ground over springs 3 of key SK. The ninth contacts are grounded over springs 1 of key I SK so that if, as shown, no strapping is provided nine impulses are sent in each rotation of the switch. The tenth terminals are directly grounded for a purpose which will be clear from the subsequent description. In

the drawings the fast and slow impulse contacts have for simplicity been shown of equal length and spacing, but itwill be understood that in practice the terminals in rows a and c are shorter and more closely spaced than those in the rows 6 and 6. Four contacts 1 to 4 provided at the end of the row a are used for counting the impulse series as will be described subsequently.

Assuming that the key EK has been thrown for fast impulsing, the brushesa, and c are connected up and impulses are transmitted over the loop by the brush 0. When nine impulses have been sent relay Dr is energized over the brush a, locks up over its contacts Dr2 and theoff-normal contacts N and at contacts Drl, short-circuits the impulsing brush 0 and contacts for the remainder of the rotation. W hen the brush (Z engages the con tact 4t relay Jr is energized, looks over contacts Jr3, and at contacts JrQ prepares a circuit for relay 19". On the switch arriving in its normal position relay Dr is unlocked and during the next rotation of the switch a second series of nine impulses is sent and when the brush (Z engages contact 3 relay Ir locks energizes and prepares the circuit of relay Hr. In a similar manner two further impulse series are transmitted during third and fourth rotations of the switch, relays Hr and Gr respectively becoming locked energize at the end of these impulse series. Relay G1 at contacts Grl opens the original circuit of the power magnet IP, but the switch IF continues to drive to its normal position the circuit for the magnet IP being maintained over the front contacts of relay Pr which is energized over the off-normal contacts N.

The switch IF normally sends four series of impulses as described above to set up a connection to a testline such as ITL accessible to a final conversation switch. If, however, the key SK is thrown the impulse switch IF is caused to transmit the two series of im-. pulses necessary to complete a connection to a special service test line. The first impulse series corresponds to the digit 0 and the second is determined by a strapping between the terminals X and Y. By throwing the key SK to ground is removed from the ninth contacts in rows a and Z2 so that ten impulses are'sent in the first rotation, relay Dr not being energized until the directly grounded tenth contacts are engaged. The opening of springs 2 of key SK makes the circuit of the magnet 1]? dependent upon contacts 1 of relay Tr. During the second rotation ground is connected over contacts Jrl and over a strapping XY to a certain terminal in the contact row a or Z) and when at the end of this rotation relay I1 is energized it opens the original circuit for the power magnet I? which however is maintained energized over front contacts of relay Pr until the switch reaches its normal position.

When the impulses have been sent the routine test circuit waits for the completion of the test calll When the test line is seized a slow release relay R7 operates over the backward loop and breaks the forward loop contacts Pwl thereby initiating the release of the switches in the connection. It a special service test line is used a further relay similar to relay R?" will be provided having its contacts connected in series with the relay R4 so that the energization of either relay will cause release. When the booster metering current is connected to the 0 wire relay Mr operates and unlocks all the relays in the routine test circuit with the exception of relay Ar.

When relay Cr relapses a circuit DKQ, C 1 3, AK2, T11, is closed for the power magnet PF which drives the switch T'F. On the brush (Z leaving the terminal on which it is standing relay A1 is unlocked and relay Tr is again connected to the contacts in row (Z and again becomes energized when the brushes are properly centred on the next terminal set. The test new begins again as previously described.

It the routine finder circuit is stopped on a busy second finder, key DK may be depressed to unlock relay Cr. \Vhen the key DK is released ground is reconnected to the power magnet PF which drives the switch TF to the next line finder terminals.

For advancing the switch TF to particular second line finder circuits a set of tens keys TX is provided for earthing the first terminals in the tens groups of contacts in the row 6 of the switch TF and a set of units keys UK is provided for earthing the units contacts in the tens groups in this row. To test a determined second line finder circuit, say that the number of which is 25 in the 100 group serves by the routine test circuit, the tens key TK21 and the key CK are first thrown. The key TK21 applies ground to the 21st contact in the row 6 whilst the key CK completes a circuit via AK3, Trl, for the power magnet PF. lVhen the brush 6 reaches the 21st terminal, relay T1 energizes over brushes 6 and (Z, and contacts Ar2, locks over contacts T'73 and key CK, lights supervisory lamp TL over contacts T14, and at contacts Trl opens the circuit of the magnet PF. The keys TKQl and CK are then released. The relay T9" remains energized and holds open the circuit of magnet PF until both keys TK21, CK are restored. The release of key CK opens the original circuit for magnet PF. Keys UK5 and CK are next thrown,

the circuit for magnet PF is again closed is energized over springs 1K2 and locks via M1 1, 1K1. The test proceeds as already described and on the energization of relay M1", relay Cr relapses but no driving circuit is closed to advance the switch TF. l/Vhen relay Mr ale-energizes relay C7 again operates and the test is repeated on the same line finder circuit. The test is repeated in this manner until the key 1K is released.

A ack MJ is provided into which the test clerk can plug to check the transmission of dialling tone from the register controller. By plugging into the jack MJ before throwing the key IF the clerk connects his headset across the a and 5 ot the test line TL wires and is able to hear the dial tone. The opening of the springs MJl and MJQ disconnects the power magnet IP and opens theimpulsing loop thereby preventing the operation of the switch IF until the plug is removed from the jack Md.

The line condition may be changed by the aid of keys GK, HK, and J K through the medium or" which a 20000 ohm leak, a 1000 ohm line and an extension set respectively may be introduced on the test line.

The test circuit may be used to test more than 100-line finder links by providing two or more switches such as TF the wires from the brushes of which may be connected to the test circuit over suitable keys.

The operation of the testing circuit shown in Figure 3 will now be described.

Automatic test of concersate'on group selector finders and common control circuits The starting key QAK is thrown and provided the test circuit finder TGF is centered on the contacts of a group selector finder the relay 2T1" is energized over a circuit, QAK L, brush (Z of switch TGF and bank contact, QAJQ, and completes a circuit for relay 2137' over 215-7 3, 2012, QDKQ, 2am, ens, sans, winding of relay 2B1 and brush c of the switch TGF. Relay 2B1 operates to the battery applied to the 0 wire it the group selec tor and its associated control circuit are free, and closes a circuit for relay 261 which extends from battery over winding of relay 2C contacts 2Br1, home contact and brush of bank of a control switch HTS, 2Cr67, 2AK5-4 to ground. Relay 2Cr locks up over contacts 20%? and 2Grl in parallel and its make before break contacts 2Cr6. A lamp 23L is lighted over a parallel circuit to indicate that the switch TGF is centered on the contacts of an idle group selector.

Relay 2G7 closes a circuit 20ml, 2015- 1: for relay 2A1" which locks over its contacts QArl and disconnects the test relay 2T Relay QCrat contact 2Cr5 also connects ground via contacts 2071 to the 0 wire there by rendering the engaged group finder switch busy, and at contacts 2&4 closes a circuit 201 1, 2Cr54, Nrl, M7 1, U15 for relay K1".

Relay Kr connects battery to the a wire of the fundamental circuit via contacts K'r1,Dr1 and ground to the 6 wire via contacts KrfZ, winding of relay Pr, Dr5, 2076. The control circuit associated with the group selector finder under test is thereby taken into use as fully described in our U. S. application 370,673 and three selections are made one in the group selector and two in a final selector, the relays K1 ll 1', P1, R1", N7, SW, Q2", Dr functioning substantially in the same manner as the likenamed relays in the register-controller in the application referred to. When the control circuit associated with the group selector becomes attached to the latter, the outstepping relay Pr is energized over the 5 wire and closes a circuit via contacts Mrg for relay R1" which closes a circuit RrQ, QCrl-5 20r1 for relay N1" and at contacts RTE) connects the outstepping relay Pr in a metallic circuit across the a and 6 wires. Relay N1" opens the circuit of relay Kr.

The group selector control switch now advances its brushes to mark a wanted group of trunks in the bank of the group finder and sendsrevertive impulses to short-circuit the relay Pr, at each relapse of which a circuit is closed via contacts R4?) for relay Q1", which closes a circuit for the stepping magnet 2R6 of the register switch RTS and holds over its contacts Qrl and the interrupter springs of the magnet 211T to maintain the circuit of the magnet, even if relay Pr should open its back contact before the magnet 211T is fully energized.

In the present case it 'is assumed that the first selection corresponds to the digit 5. The first four contacts in the are a of the switch RTS are therefore strapped together and jumpered to the contact 2 of relay U1. The first selection may obviously be varied to meet requirements by changing the strapping of the bank a. Then the relay R1" was energized it locked up over its right-hand winding, contacts R74, Vr5, UrQ are strapping and brush a 2Cr4-5 and 2014.

lVh en the switch RTS arrives in position 5 the holding circuit for relay R1" is opened and on the next relapse of relay P1" the relay R1 relapses, opens the fundamental circuit and deprives relay N7 of current. Relay N1" being of the slow-to-release type remains in its front contact NrQlong enough to cause the energization of relay S1" via contacts Rrl. A series circuit is now closed for relays Mr and Q1" extending over are contact and brush 6 of the switch RTS, Url, SW1, NrQ. Relay Q9" energizes the magnet- QRT of the switch RTS whilst relay Mr at M14 recloses the fundamental circuit and locks over MrQ, P1 2. l/Vhen relay S1 relapses relay Q1" deenergizes and the switch is advanced to position 6 in which relay Ur is energized via Vr6 and brush a, looks over contact Uri), connects ground to the first contactin the arccof switch RTS over contacts Url, opens the circuit of relay K1" at contacts Ur5, and at contacts UM closes a restorin circuit for the magnet QRT of the switch RT When the brush 0 engages the first contact in its arc, relay Vr energizes locks over V773 and unlocks relay U1" which opens the circuit of the magnet ZRT and reestablishes the circuit of relay Kr.

During the opening of the fundamental circuit between the relapse of relay R1" and the response of relay Mr, the hunting operation of the groupfinder is initiated,as fully described in the U. S. application previously referred to.

When relay Kr re-operates it initiates the second selective operation as before, relay Br being locked up via RM, Vrl and contact and brush (Z of the switch HTS. The switch RTS is stepped as before by revertive signals from the final selector switch. When the switch RTS arrives in position 5 the locking circuit for relay R1" is opened at are (Z, the circuit of relay N1" is opened and between the relapse of relays R7" and N1, relay S1" is energized as before. Before the relapse of relay Nr a circuit Xrl, brush 6, VrQ, Srl, NW2 is closed for relay Q0 and when relay N1" falls off the switch RTS is driven to position 6 in which relay X1" is energized overbrushcand contacts Vr3, locks up over X7 3 and prepares a circuit for relay D1" at Xr2.

The final control circuit finder is driven in this manner to terminal set number 71 and as the otherwise unused terminal set marked H1 in Fig. 9 of the U. S. application referred to is used for test calls eleven steps are required at the final control circuit for units selection. It should be noted that after the tens selection the switch BTS is not restored stepping for the units selection beginning at position 6.

When the relay R1" relapses it opens the fundamental circuit to initiate group selection y the final selector switch and when relay N1 falls back a circuit Ur5, Mrl, Nrl, is closed for relay Kr which closes a circuit for relay P1" over the 6 wire in series with the instepping relay at the final control circuit The relays R1", N1 now respond as before the relay Rr reclosing the fundamental loop over the a and 5 wires; l w

The switch RTS now makes ten steps in response to revertive signals and in arriving in position 5, relay R1" is unlocked and relay S9" energized. A circuit is then closed for relay Dr (over brush 6, Vr2, SP1, NW2) which locks over Dr?) and connects the a and 6 wires to the windings of relay 201 over contacts Dr2, D14.

If the final selector switch has tested the correct line QTL, relay 2E1 is energized and when the metallic through connection becomes established relay 2Fr and .201 energize in series and a circuit is closed for relay 2G1. Relay 2C?" is thereby unlocked, closes a subscriber removes his receiver.

a restoring circuit for the switch RTS and opens the locking circuit of all the operated relays except relay 2A1".

The a and l) wires are now disconnected and the group and final selector switches are released. Relay 2Er relapses and closes a circuit 2Er3, 207 2, 2DK2, QAKl, 2Tr1 for the power magnet QPF which advances the switch TGF. Vhen the brush d leaves the terminal on which it was standing, relay 2Ar relapses and connects up the test relay 2Tr which energizes and arrests the switch TGF when it reaches the next contact set. Lamp 2TL. is again lighted and the test is repeated on the next group selector provided it is free.

It the group selector or its control circuit is busy, relay 2Br does not operate and the lamp QBL does not light. By momentarily depressing key QDK the relay 2A1 is energized, looks over 2Ar1 and de-e-nergizes relay 2Tr which recloses the driving circuit for the magnet QPF. When the switch TGF leaves the position in which it is standing relay 2A? is unlocked and again connects up the test relay 2Tr.

If a final selector in response to a test seizes a line other than the test line QTL, relay 20r becomes energized when the called As relays 2Fr and 2Er are not energized, relay 2Cr is not deenergized but all the remaining relays except 20r and 2A9 relapse and relay 20r remains held over 20r2, 2Er1. The chain of switches is therefore released and the called subscriber is freed, but due to the fact that relay 2Cr is maintained operated the switch RTS is not restored, and the switch TGF is not advanced. The lamp QBL remains lighted. A key QPK is provided which when thrown short-circuits a resistance to vary the line conditions over the fundamental loop circuit.

Rapid test of control circuits lVith the key QEK depressed the test relay 2Tr is only connected to the first terminal of each set of ten terminals in the row d of the switch TGF. "When therefore the key QAK is thrown, the switch TGF is arrested on one of these terminals and on the completion of the test the switch TGF is advanced over the nine intermediate positions to the next tenth terminal and tests the control circuit assoq ciated with another group of ten group selector finders.

Test of a determined group selector switch TWO sets of keys QTK and QUK are provid ed for grounding respectively the tens and a QPF which advances the switch. TGF to position 11 in which the test relay 2TB is operated over key 2TK11 and brushes e and d to arrest the switch and light a supervisory lamp QTL. Relay 2T1 is locked over 2Tr3 and key QCK and releases when both keys QCK and 2TK11 are restored.

Keys QUKG and 20K are next depressed and the switch TGF is again advanced until relay 2T1 is energized in position 16 and again lights lamp 2TL.

The test clerk now releases keys QUKG and QCK and throws key 21K to start the test which proceeds as already described. On the relapse of relay 2Er however no circuit is provided for the power magnet QPF of the switch TGF which remains on the same group selector. Relay 2Br however is again energized and recloses the circuit of relay 2C1 which causes the test to be repeated. The test is repeated on the same group selector until key 21K is restored.

The test circuit, Fig. 4 for testing the final selector switches and their associated control circuits operates in substantially the same manner as the circuit shown in Fig. 3 with the exception that the register switch 3RTS is adapted to respond to two series ofrevertive impulses only.

Automatic test of conversation final selectors and control circuits When the starting key SAK is thrown provided the brushes of the switch TFF are properly centred relay 3Tr is energized and if the final selector and its associated control circuit are free, relay 3Br operates and closes a circuit for relay 3Cr via brush 6 of the switch 3RTS. Relay 3Cr locks up over contacts 3Fr2 and 80r8 in parallel, energizes a relay 3H? and closes a circuit for relay 3A1" which disconnects relay 3T7". Relay Kr is also operated and connects battery and earth to the a and l) wires respectively over brushes a and l) of the switch T'FF.

The relays Kr, Rr, Sr, Nr, Gr, Pr and Dr function in the same manner as correspondingly-named relays in Fig. 3.

The switch 3RTS is arranged to so control the tens and units selections of the final selector that the latter is directed to a test line 3TL which extends back to the routine test circuit. In the present case it is assumed that this line is reached by making ten steps for the tens selection and eleven steps for the units selection the wipers of the final control finder being directed to the otherwise unused terminal set indicated H in Fig. 9 in the U. S. application referred to. The switch 3RTS is not restored between the two selective operations.

The revertive impulses of the tens selection cause relapses 0t therelay Pr, as in the arrangement shown in Fig. 3. In position 10 the holding circuit for relay Rr, (over brush a) is opened and on the next relapse of relay Pr the relay R1" falls away and opens the fundamental circuit to send the necessary signal to the final switching stage to commence the unit selection. Between the relapse of relays Br and NW, relay S7" is energized and closes a circuit for relay Q1 and on the relapse of relay N7 the switch 3RTS is driven to position 11 in which the relay 3Vr is energized over the brush 7), looks up over its inner right-hand contacts and prepares circuits for relays D1" and 31%.

On the relapse of relay N1", relay Kr again energizes and closes a circuit for relay Pr over the 6 wire of the fundamental circuit in series with the instepping relay at the final control circuit. Relays Br and N1 now energize again and the fundamental loop is reclosed over a and 7) wires.

The units selection. now takes place, reverti e signals causing the switch 3R-TS to e stepped to position 10 in which relays Br and N1" are de-energized and relay S1" is energized asbefore. Relay Dr operates over brush 0, looks up, lights a supervisory lamp CL, and connects the 6 brush of the switch to the right-hand winding of relay 301" via contacts Dr, 301%.

Provided that the final selector switch has been advanced to the test line 3TL relay 3E7 is energized over the'test wire, and relay 3X1" is energized over the ground connected (over contacts F374, 6 shown in the U. S. application referred to) to the a wire in the final finder switch. Belay 3X1" locks up and its 1 contacts 3X13. at contacts 3X11 bridges the ringing relay 35. and condenser C across the a and 7) wires and at contacts gari connects the left-hand wind ng of relay to the a brush of the switch TFF via contacts Dr2.

When the relay 3dr responds to the trans- I mitted ringing current it closes a circuit for i closed over back contacts of a slow release relay 3G7", which short circuits the winding ofslow-release relay 3H1 which relapses and completes the circuit of relay 3F?" which looks up at contacts 31*? 1, at contacts 12 opens one looking circuit of relay 3C?" and at contacts 31%?) bridges an 1100 ohm resistance R2 a cross the ringing relay 351" and condenser C thereby causing the final selector ringing relay to operate and establish the metallic throughconnection. If a tele phone set has been plugged into the jack LJ the ringing tone can be checked. Relay 301" is energized over the line, extinguishes the supervisory lamp CL, and releases relay 361 which closes a restoring circuit for the switch 3RTS and unlocks all the operated relays in the test circuit except relay 3A7. The circuit of the power magnet- SPF of the switch TFF relay 8E7" so proving that the final selector has been released. Relay 3A1" relapses when the switch TFF advances and relay 3T? energizes when this switch. is correctly centred on the next terminal set. Lam QTL is lighted and the test is repeated on the next final finder provided it-is free.

- he purpose of the slow-release relays 3G1; El-lr. 3?? is to prove that the ringing relay of the final selector under test does not o-pcrate over the 8000 ohm resistance R1 which is normally bridged across the relay 3d? and condenser C. If this happens the metallic through-connection is established before the relapse of relay 3E7". Relay 3G7 energizes, removes the ground from the 0 brush of the switch TF1? and so releases the final selector. Relay SE?" therefore (lo-energizes and provides a locking circuit for the right-hand indin of relay 301. The relay 3G1" re mains looked over contacts 3Fr2 and the lamp 3BL remains lighted.

If the final finder under test is incorrectly brought-to a free subscribers line the relays 3E7, 3G? are not energized but when the called subscriber answers the bridged relay 3G1" energizes, releases the final selector and frees the subscriber by removing ground from the 0 brush of switchTFF. The relays 301' and 3C? remain locked up however and the lamp 33L lighted as described in the previous paragraph. The switch 3RTS does not restore and a new test cannot be started.

A key SDK is provided for causing the advance of the switch TFF if it stops on the contacts of a busy final selector. The operation is the same as in the arrangement described with referenceto Fig. 8.

The line conditions over the fundamental circuitmay be varied by means of a key 3PK as in the arrangement shown in Fig. 3.

Test of a determined final finder switch and rapid test of control circuits These tests may be elfected in the same manner as in the circuit described with reference to Fig. 3, the keys ZTK, 3UK, 3EK, 31K, 3EK controlling the operations in the same manner as correspondingly-named keys in that figure.

Test for busy condition The response of a final selector to a busy condition may be tested by throwing keys 313K, 3AK. Key 313K removes the battery applied over relay 3BR from the third wire of the test line 3TL and substitutes ground, bridges the positive and negative terminals, and connects the left-hand-winding of relay 30?" to the a brush of the switch TFF. As soon as key 8AK is thrown the cycle of operations starts and is completed as described for the automatic test, but when the test line STL is seized. the rin ing relay 3J7 and the bridge relay 30? are not operated and relay 3C1" is not released; and the lamp CL remains lighted. A telephone set can be plugged into the listening jack LJ and the busy tone checked. The release of the keys 313K. 3AK restores the test circuit.

hat is claimed is:

1. A telephone system comprising a plurality of selector switches, common control circuits therefor, and a testing arrangement adapted to be associated with any one 01 said switches said arrangement being adapted to perform automatically a series of operations on one of said switches and a control circuit associated therewith, which operations are similar to those which would occur in the setting up of a connection to a wanted line by means oi said switch and said circuit.

2. A telephone system comprising a plurality of selector switches, a plurality of common control circuits each adapted to be associated with any one of said selector switches, and a testing arrangement and means for successively associating said testing arrangement with said selector switches having different control circuits connected thereto whereby routine tests may be automatically carried out.

3. A telephone system comprising a test line, a plurality of numerical selecting stages, a plurality of conversation switches in each stage, common control circuits for said conversation switches, test circuits adapted to test the apparatus at each numerical switching stage, and means associated with said test circuits for taking into use in turn each one of said conversation switches and for automatically extending a connection thereover to said test line.

41. A telephone system comprising a plurality of selector switches, common control circuits adapted to be associated with and to control any one of said switches, a test circuit, a device associated with said test circuit to indicate the operation of circuits and switches which may be associated therewith, and means associated with said testing circuit adapted to operate one of said switches to a predetermined position to cause the operation of said device.

5. A telephone system comprising, a testing circuit, a plurality of link circuits, each of said circuits comprising a backwardly hunting finder switch and a group selector switch, a first test line, a second test line, means for controlling the advance of said finder switch to said first test line and for subsequently exercising control over said first testline to cause a connection to be extended over group selector switch to said second test line, said second test line extending back to said testing circuit.

6. A system according to claim 5 wherein said first test line is connected to a contact in the bank of said finder switch, means being provided adapted to apply a calling potential plying a calling potential to said first test line and to cause said finder switch to hunt therefor, and means for preventing the application of said potential to said first test line and the operation of said finder switch in the event that another one of said plurality of finder switches is in operation when the test is initiated.

8. A system according to claim 5 comprising an automatic impulse sender adapted to transmit series of impulses for controlling the extension of the connection to said second test line.

9. A telephone system comprising, a testing circuit, a plurality of link circuits, each of said circuits comprising a backwardly hunting finder switch and a group selector switch, a first test line, a second test line, means for controlling the advance of said finder switch to said first test line and for subsequently exercising control over said first test line to cause a connection to be extended over said group selector switch to said second test line, said second test line extending back to said testing circuit, an automatic impulse sender adapted to transmit series of impulses for controlling the extension of the connection to said second line, a registering and controlling mechanism adapted to be as sociated with a link circuit, and means adapted to delay the transmission of said impulses until said mechanism has been connected to said link.

10. A telephone system comprising a plurality of switching stages, a plurality of conversation switches at each such stage, a test line having a device associated therewith which is adapted to be operated when said line is seized, and a testing circuit comprising operating means under the control of which a connection is adapted to be extended over one of said switches of one of said stages and over one of the switches of a succeeding stage to said test line.

11. A telephone system according to claim 1, having an automatic switch over whose brushes said selector switches are adapted to be tested, and a switching device adapted to be operated on the completion of a successful test to cause the test connection to be broken down and to cause said automatic switch to advance to a succeeding selector switch.

12. In a routine test circuit comprising an automatic switch over whose brushes selector switches are adapted to be tested, and a switching device adapted to be operated on the completion of a successful test to cause the test connection to be broken down and to cause said automatic switch to advance to a succeeding selector switch the combination of means adapted to cause a cessation of the testing operations in the event that said succeeding selector switch is busy.

13. A system according to claim 2 comprising means for subsequently causing the testing operations to be continued.

14. A telephone system comprising a testing arrangement having a switching device, a subscribers line, a plurality of selectors arranged in selecting stages for making a connection to said line, common control circuits for the selectors belonging to each one of said stages, and means whereby said testing arrangement is adapted to set up a testing circuit to said subscribers line over said selectors, said switching device being adapted to be operated on the reply of the subscriber to initiate the release of the switches engaged in the connection.

15. A telephone system comprising conversation switches, common control circuits therefor, a testing circuit, a test line adapted to be extended between said switches and said testing circuit, means for associating said testing circuit with said conversation switches in a predetermined order, a signal device in said testing circuit and means adapted to cause the operation of said signal device when a conversation switch associated with said testing circuit is positioned on said test line.

In witness whereof, we hereunto subscribe our names this 2nd day of February, 1930, and 3rd day of February, 1930.

GERALD DEAKIN. EDOUARD FRUM, Legal Administrator of the Estate of Lz'pa Polz'nkdwslcy, Deceased.

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