US2082104A

US2082104A - Testing system

Info

Publication number: US2082104A
Application number: US58312A
Authority: US
Inventors: Earl S Gibson; Arnold A Hansen; John B Worth
Original assignee: American Telephone and Telegraph Co Inc; Bell Telephone Laboratories Inc
Current assignee: AT&T Corp
Priority date: 1936-01-09
Filing date: 1936-01-09
Publication date: 1937-06-01
Anticipated expiration: 1954-06-01

Description

June 1, 1937. E s. GIBSON ET AL 2,082,104

- VTESTING SYSTEM Filed Jan, 9, 1956 2 Sheets-Sheet l TToRA/Ey Jun e 1, 1937. E. s. GIBSON ET AL 2,082,104

TESTING SYSTEM Filed Jan. 9, 1936 2 Sheets-Sheet 2 SLi-'N m S@ E. s. @Isso/v g g 3 /NvE/v ro/gs.- ,4.4. HANSEN N N N J. B. WORTH `ATToRNr 'Patented June 11.937'v UNITED STATES PATENT OFFICE TE STIN G SYSTEM York Application January 9, 1936, Serial No. 58,312

Claims.

This invention relates to testing systems and more particularly to systems for timing the duration of ringing signals received over a telephone line.

In toll line systems considerable time is frequently lost due to the failure of signal receiving apparatus to operate on the ringing signal impulses transmitted over the line by a distant operator. Toll operators are usually instructed to impress ringing current on a line for approximately two seconds which, it has been determined, is sufficiently long in most cases to cause all line apparatus to function. It no-w appears, however, that under adverse conditions, either normal or transient, the signal receiving apparatus of some lines occasionally fails to operate on a two-second ring and, therefore, it is desirable to determine, by suitable tests, the actual time required to cause proper functioning of the signal receiving apparatus associated with such lines.

An object of the invention is, therefore, to determine the approximate over-all ringing margin of a given telephone line, i. e., the duration of the received signal. In other words, to determine the duration of that portion of the original signal which is received at the distant end of the line after all intermediate apparatus in the circuit has functioned.

A feature of the invention whereby the foregoing object is attained, resides in the provision of two duplicate test sets which are connected to opposing ends of a line to be tested and so arranged as to alternately and automatically send and receive definitely timed ringing signals over the line. With such an arrangement the test setv at one end of the line, when initially started by an attendant, sends out a definitely timed ringing signal which, if received by the test set at the other end of the line, causes a visual indication to be there given of the duration of the signal which is received, i. e., the margin of the transmitted signal over and above that required to cause any intermediate and terminal signal responsive apparatus to function. This margin may, in' the case of a two-second ring, amount to one second, more or less, depending on the character of the line and the apparatus associated therewith, which delays the transmission of the signal. When the second test set has received, timed, and visually indicated the length of this marginal iinpulse, it returns, after a shortdelay, a similar timed ringing signal tothe rst test set which then functions to receive, time, and indicate the length of the signal impulse which reaches it in a similar manner to that described for the second test set above, after which it in turn initiates another timed outgoing ring to the other end of the line. In this manner, the two circuits continue to alternately send and receive signals as long as signals of a predetermined length are received at both ends of the line. If a signal is received by either test set which is shorter than a predetermined minimum length, the test stops.

A further subordinate feature is the provision of means whereby the length of a ringing signal transmitted by either test set can be varied as desired.

Another feature resides in means whereby, following the transmission of a signal, the test set circuit is held in abeyance for an interval sufficient for the return signal from the other end to be received. If this return signal is not received, the circuit restores to normal.

A further feature resides in a novel timing arrangement employing ltwo hot cathode gas-filled I f tubes which are so arranged and adjusted that the control electrodes regain control of their respective tubes and stop the discharge upon attaining a predetermined negative potential. The potentials of the grid are controlled by a condenser-resistance arrangement which may be easily adjusted for slow or fast tube operation by either increasing or decreasing the resistance.

The invention will be understood from the following deseription when read in connection with the accompanying drawings:

Fig. 1 of which, to the left of the broken line AA', represents a `typical Voice frequency signaling toll line TL, employing 1000 'cycles interrupted at the usual ringing frequency of cycles, which line terminates at a toll operators position in a jack I 00. In this same figure, but to the right of the-broken line AA', is shown a multiple jack |0| of this same toll line located at a. test and control board together with a ground jack |02, battery jacks |03 and |04, patching cords |05 and |06, ||0 and l| |,and an abbreviated schematic of one end of a toll cord |01 of a type adapted to function with toll lines such as TL; and

Fig. 2 shows, to the right of the broken line BB', the wiring and apparatus of the test box of the invention and to the left of the broken line a plurality of jacks 20|, 202, 203, 204 and 205 also located at the before-mentioned test and control board to which jacks the test box may be connected by wires 206 in case it is desired to Alocate the test box at some point distant from the test and control board, but from which point the test is to be controlled.

For the purpose of describing the invention, it will be assurned that the toll line TL (Fig. 1) is to be tested as to the length of ring necessary to transmit thereover in order to operate the lockup relay it@ which controls the line lamp IUS or the sleeve circuit of a connected cord and that the person conducting the test, hereinafter called the tester, has elected to locate the test box at, and control it from, the test and control board at which the line appears in multiple jack IUI, it being understood that the test can be made in the same manner if desiredat the toll switchboard where the line also terminates in jack |60.

With the foregoing assumption the tester places the test box in some convenient place on or near the keyshelf of the test board and connects the line jack Iil to the test box line jack 269 by means of a simple patching cord it and patches, by means of cordsI Ii) and I I I, the battery jacks IES and Illi to jacks 2'I and 208 of the test box. v

lt is also necessarythat a duplicate test boX similar in every respect to the box shown on Fig. 2 be connected to the distant end of the toll line in the same manner as just described for the near end of the line. v

A detailed description of the operation of the invention will now be given by first describing the functioning of the interrupter circuit I, which transmits current pulsations over lead 209, through the winding of relay 2li) which responds in unison with said pulsations.

rThe gas-nlled ionic tubes 2i l and 2 l2 are of the type in which the grid elements 2I3 and 214 can control the deionization as well as the ionization of the tube, that is to say, after the tubes are ionized a sufficient reduction in the potential 0f the grid elements 2L?, and 2M in respect to the corresponding cathode elements 2I6 and 2I5 results in deionization.

The cathode elements 2I5 and ZIB are connected in series and are energized in a circuit that is traced from the upper terminal of battery IIR, through the tip conductors of jack |83, patching cord il@ and jack 267, over conductor 2l?, through operated contacts of relay 2I8, cathode elements 2I5 and 2l6 in series, through fixed resistance 'M9 and the multiple resistance path consisting of a fixed resistance 220 in series with a rheostat 22I, over conductor 222, through tip conductors of jack 268, vpatching cord III and jack HIM to the lower terminal of battery I I2. Relay 2&8 is operated in a circuit Yfrom ground through the winding of relay 2I8, over conductor 222, through tip conductors of jack 238, patching cord ill and jack 25M to the upper terminal of grounded battery H3. When relay 223 operates, as will be hereinafter described, positive ground 22T: is connected through its lower outer contacts to junction point` 225, whence the circuit to anode element 225 of tube 2I2 is completed through resistance 22T and the winding of relay 2W, and to anode element 228 of tube 2 l I through resistance 22S. Due to voltage drop, the potential difference between the cathode element iii and the anode element 225 of tubeVZI?. is greater than the potential difference between the cathode element Ziii and the anode element 228 of tube 2H. Consequently, when the circuit through the cathode elements 2I5 and 2Iii`is closed, as before described, and both tubes start to heat at the same time as a result of the greater anode-cathode difference oi" potential in the caseof tube 2 I2, this tube ionizes before tube 2i I.

Assuming then that tube 2 I2 ionizes rst, there will be an immediate drop in the potential of thel lower terminal of condenser' 2333, due to the current flow in resistance 22E and the winding of relay 2I, which will be transmitted through condenser 236) to the grid EIS of tube ill i, causing the potential of grid 263 to be reduced correspondingly and to 'assume a negative value thereby preventing the immediate ionization of tube 2II. Due to the proximity of the grid 2M of tube 2I2 to its cathode elementY 225, the potential of grid 2M is slightly higher than that of the cathode 2I5 and the ionization of tube 2I2 is thereby maintained. A current will now iiow from the higher positive potential of the grid 2M, through the Variable resistance ZSI, lower outer normally closed contacts of relay 2F15 to the upper terminal of condenser 23D which is connected to the grid 2I3 oi tube 2I I. After a short interval the charge of condenser 235i will be adjusted so that the potential of the grid 2I3 equals that of grid Consequently, tube 2li now ionizes and there will oe an immediate reduction in the potential of the right-hand terminal of condenser 233 due to now ofcurrent through resistance 229. This reduction in potential is transmitted through condenser 23,causing the potential of its left-hand terminal to be reduced correspondingly. Since tl is left-hand terminal is connected to the grid 2id which, as hereinbefore state-1l, is at a potential only slightly more positive than the cathode element ZIE of tube 2I2, grid fil now assumes a negative potential, causing the immediate deionization of tube 2I2. Due to this deionization, current through the anode circuit of tube 2I2 ceases and condenser Zt is now charged to nearly full battery potential as was condenser when tube 2I2 was ionized. Condenser immediately after being charged, as before stated, now begins to discharge through tube 2i I, and through the lower outer operated contacts of relay 2% and variable resistance ZS to grid 2 M, thereby raising the potential of grid 2M to a positive value equal to that of grid 2l3 of tube 2li and causing the ionization of tube 2li?, Immediately afterwards, tube 2l l is again ionized, as before described, and the cycle of ionization and deionization continues automatically. By varying the setting of the variable resistance Ztl, the cyclic speed may be varied. Increasing the resistance reduces the frequency of the interruptions, and vice versa.

The operation of the interrupter I having been discussed, the operation of the other features of the invention in conjunction with interruptor I will now be described. Let it be assumed that the toll line TL has been connected with the test set of Fig. 2, as before described, by patching the test and control board jackv lill by cord IE5 to jack 2%. When the plug II 4 of .patching cord H35 is inserted into jack. Zilli, the contacts 234 are closed, operating the relay 223 through a circuit from battery through the winding of'relay 223, lower back contacts of relay 235e', upper break contacts of key 23% to ground through contacts 231i. Relay 223 connects ground 22:3 at its lowermost contacts to the interruptor circuit I, as before mentioned, in order to complete the anode circuits of tubes 2l! and 2I2.' As before described, these tubes now start to ionize and deionize alternately. Relay 2 i il operates when tube 2i2 ionizes, but at this time relay 2 l El has no function. In order to start the circuits to functioning Ult 'through transformer |45 v*to the grid circuit of the start Jkey 23T-of the test set is operated, which operates relay 238 in a vcircuit from battery through contacts of key 231, upper winding of rela-y 2-38 to ground on the upper middle contacts of relay 239. Relay 238, in operating, connects cattery 249 through the uppermost normally closed contacts of relay 24|, resistance 242, upper middle make contacts of relay 238, tip contacts of jack 4200 and plug I |4, over tip conductor of patching cord |05, through tip contacts of plug ||5 and jack |0| to the ltip conductor ||6 of the toll line TL. From this conductor, the circuit is continued through the winding of retardation coil |1`and relays ||8 and ||9 to ground. Relay ||9 now operates, releasing relay |19. Relay I9 is normally operated in a circuit Vfrom ground through its winding, upper outer break contacts of relay 10 and resistance |82 to battery. When jack 200 was patched to jack |0|, relay |10 operated, as will be hereinafter described, releasing relay I I9 and lighting busy lamp |84 from battery through its upper front contacts. The release of relay |19 removes the short-circuitaround the series transmission pads `consisting of resistances |15, |16, and |8| and disconnects the shunt pad consisting of the condenser |18 and resistance |11 in series. Relay ||8 also operates and connects b-attery over lead |20 and through back 'contacts of relay |2| and winding of relay |22 to ground. Relay |22 operates and transfers, with its upper and lower outer armatures, line conductors |23 and |24 to ringing conductors |25 and |26, respectively, which connect through resistances |21 and |28 to the source |29 of Voice frequency signaling current generally arranged to deliver current at 1000 cycles per second. Relay |22, in operating, also koperates relay |30 in a circuit from ground on the upper inner contacts of relay |22 through the winding of relay |30 to battery. In operating, relay |30 disconnects with its left-hand contacts leads |3| and |32 of the signal receiving circuit and with its left-hand cont-acts bridges the ringing termination resistance |33 across conductors |25 and |26. 1000 cycle current is now transmitted through .the operated upper, outer and lower front contacts of relay |22,- over conductors |23 and |24, thro-ugh right-hand windings of repeating coil |34 and condenser |35, thence by inductionthrough the left-hand windings of repeating coil |34 to the outgoing line conductors |36 and |31 and thence to the distant telephone oice at which apparatus equivalent to or identical with that shown on Figs. l and 2 is installed. Let it be assumed now that in response to the outgoing signal that an incoming signal of 1000 cycle current is received over the toll line. A description of the functioning of the distant apparatus whereby this responsive signal is produced and transmitted will be available from the description of the operation of the apparatus of Fig. `1 and Fig. 2 hereinafter to be given. The incoming signal aforesaid is received through repeating coil |34 and condenser |35, thence through the upper and lower back contacts of relay |22, left-hand windings of repeating coil |36, through back contacts of relay |30, over conductors |3I and |32, through condensers |39 and |40, resistances |4| and |42,l and the 1000 cycle tuned rcircuit consisting of condenser |43 and retardation coil |44. The condensers |39 and |40 and the resistances |4| and l'|42 are provided to raise the impedance of the circuit. The tuned circuit is provided so that only frequencies `close to 1000 `cycles 'are passed cycles.

the associated ionic amplifier tube |46. YThe cathode element |41of tube |46 is heated in a circuit from battery |48, through resistance |49, cathode |41, cathode |50 of ionic detector tube -i 5| to ground' |52. The anode |53 of tube |46 is in vseries `with the left-handwinding of the transformer I 54. In lresponse to the incoming signaling current, tube |I|6 delivers an amplified current through its anode `circuit which is passed by induction through 'the transformer |54 to the g-rid '|55 of tube |5|. In response to the input to tube I5 the direct current inthe anode circuit of tube|5| is increased from some small normal value to a much higher value. This `anode circuit is traced from anode |56 through the lefthand winding of transformer |51 to battery |58. The incoming 1000 cycle current is interrupted at a frequency of about 20 cycles per second and consequentlyl a ypulsating direct current-of this frequency is delivered to the left-hand winding of transformer |51. To remove the 1000 cycle currentfrom the anode circuit of tube |5| a shunting condenser |59 of small capacity is used. n response to the 20 cycle input current, an alterhating current is induced in the right-hand winding of transformer |51 through the winding of polarized relay |60, which therefore operates at a 20 cycle rate. When the armature' of relay |60 makes its left-hand contacts, as shown in the f drawings, there is a flow of charging current from battery through upper winding of relay |64, lefthand contacts of relay |60, condenser |63 and retard coil |62 to ground therebyy charging condenser |63. When the larmature vof relay |60 moves to its right-hand lcontacts condenser "|63 discharges in a circuit traced from its lower terminal through winding of retardation coil I 62, grounds 6| and |65, lower winding of relay |64, right-hand contacts of relay |60 to upper terminal of condenser |63. Condenser |63 and the winding of yretardation coil |62 are so designed asto form with the windings of relay |64 a 20 clycle tuned circuit. Accordingly condenser |63 can be fully charged and discharged only when i' the operating rate of relay |60 is close to 20 Consequently, since relay |64 is marginal, it does not operate except when the operating rate of relay |60 is Very close to 20 cycles. This arrangement is to avoid the possibility of false operation fdue to the regular voice currents on the line. AWhen relay |64 operates ground is connected to the left-hand terminal ofthe winding of slow releasing relay |66 which is thereby short-circuited and consequently releases. RelayY |66 is normally operated through'an obvious circuit including resistance |61. Relay |66 in releasing closes an obvious circuit through the winding of relay |68, which operates and thereby operates relay I2| through an obvious circuit. Relay |2| in operating connects battery over conductor |20, through back contacts of relay 8 and the lower winding of relay |08 to'ground. Relay |08 operates.

When plugs |I4 and ||5 were inserted into jacks Iv0| and 200 respectively, a circuit was closed through marginal relay 243 which is traced from Abatteryvthrough resistance 244, winding of relay 243, sleeve contacts of jack 200 and plug I I4, over sleeve conductor of patching cord throughV sleeve contacts of plug ||5 and jack|0| to ground through the winding of relay |69, which operated. Relay 243, however, did not operate at that time. When relay '|69 operated it operated relay v|10 over an obvious circuit. Relay l|08 in operating connects ground at its upper inner contacts to the winding of marginal relay |1| which is thereby connected in multiple with the winding of relay |69 through the operated lower contacts of relay |10. Marginal relay |1| functions in the case of regular toll line operation, to effect the flashing of the toll cord supervisory lamp in cooperation with relay |83 and interrupter |85. However, when the toll line TL is connected to the test box of this invention marginal relay |1| does not operate. Relay 243 now operates however and thereby operates relay 239 in a circuit traced from ground on the upper inner operated contacts of relay 223 through contacts oi relay 243 and winding of relay 239 to battery. Also, lamp 268 is lighted as an incoming ringing signal, being energized in multiple, through the upper break contacts of relay 235, with the winding of relay 239. Relay 239 operated operates relay 24| in a circuit from battery through the winding of relay 24|, upper inner contacts of relay 239, upper inner back contacts of relay 246, lower contacts of key 236, to ground on the vlower inner contacts of relay 223 now operated due to the closure of contacts 234 when plug ||4 was inserted in jack 280.

Register 241 is also operated in multiple with relay 24| in a circuit traceable from junction 248, through upper inner back contacts of key 249 and Winding of register 241 to battery. Register 241 responds to each incoming ringing signal and accordingly records the number of incoming ringing signals received during each test. Y Register 241 connects ground to conductor 256 so as to light, as will be hereinafter described, the incoming signal lamps, which are represented in part by lamps 25|, 252 and 253. Relay 24| in operating completes a circuit through the winding of the rotary magnet 254 of a selector timing switch of which the

brushes

255 and 256 with associated contact banks are illustrated.

This circuit may be traced from ground on the lower inner contacts of relay 223, through lower contacts of key 236, upper inner back contacts of relay 246, lower inner front contacts of relay 24|, upper inner back contacts of relay 238, front contacts of relay 2|0, lower contacts ci key 249, lowermost front contacts of relay 2,4 lower inner front contacts of relay 239, and winding of magnet 254 to battery. As-relay 2|0 operates and releases under control of the interrupter circuit I, selector brushes 255 and 256 advance one step at a time in the direction of the arrows. When brush 255 makes contact with associated terminal lamp 25| is lighted in a circuit traced from battery through lamp 25|, brush 255 and associated Contact to ground on the operated contacts of register 241. When brush 255 advances to the second contact another lamp, which is connected to the second contact, but which is. not shown, is lighted. In similar manner, succeeding lamps are lighted. When ringing current, incoming over line conductors |36 and |31, ceases, resulting in the release of relay |64, the re-operation of relay |66, and the release of relays |68, |2| and |08, the winding of relay |1| is disconnected from its multiple relation with the winding of sleeve relay |69. This Vcauses the release of relays 243 and 239. The lighted lamp 268 is now extinguished immediately due to the opening of its energizing circuit. The release of relay 239 opens the circuit through selector magnet 254 stopping further movement of

brushes

255 and 256. The lamp connected to the bank terminal on which brush 255 stops remains lighted for a short interval until extinguished as hereinafter described. When relay 24| operated a circuit was closed for holding relay 24| which is traced from ground on lower operated off-normal selector contacts 232 through make contacts 251 and winding of relay 24| to battery. Register 241 is also held from the ground on the right-hand winding terminal of relay 24|, through upper break contacts of key 243. The release of relay 239 prepares a circuit for operating relay 258. When relay 2|8 next closes its front contacts after the release of relay 239, relay 258 operates in a circuit from battery through the winding of relay 258, lower inner back contacts of relay 239, operated lowermost front contacts ofrrelay 24|, lower break contacts of key 249-, front contacts of relay 2 l0, upper inner break contacts of relay 238, lower inner make Contacts of relay 24|, upper inner break contacts of relay 246, lower contacts of key 236, to ground on the lower inner front contacts of relay 223. A circuit is now closed for operating relay 238 through its upper winding. This circuit is traceable from battery on the uppermost make contacts ofrelay 24 the uppermostrmake contacts of relay 258, upper winding of relay 238 to ground on the upper middle contacts of relay 239. Relay 233 operated, holds through its lower winding in a circuit traceable from battery through its lower winding, uppermost break contacts of relay 239, contacts 26| of relay 238, lower, inner, break contacts of relay 246, lower contacts of key 236 to ground on lower inner contacts of relay 223. Relay 238 operated closes a circuit for energizing the selector release magnet 259I which is traced from battery through the winding of magnet 259, upper front contacts of oil-normal springs 232, uppermost contacts of relay 238 and operated contacts 26|) of relay 24| to the operating ground on the winding of relay 24|. The selector accordingly restores to normal, releasing relays 24|, 258 and registerv 241, due to the release of the oinormal contacts 232. Also, the lamp 25| or a similar lamp, light through the brush 255, is extinguished.

Since the rate at which the interrupter circuit I operates is predetermined and known, the rate at which the brush 255 advances is correspondingly known. Consequently the length of the received ringing signal is indicated by the maximum number of lamps lighted.

With relay 238 operated and relays 24|, 258 and 239 normal, battery on the uppermost, back contacts of relay 24| is connected through resistance 242 and upper operated middle contacts of relay 238 to the tip contacts of jack 266 thereby causing the transmission of a ringing signal cutward'over the toll line conductors |36 and |31 in the manner `hereinbefore described in connection with the operation of key 231. A circuit is also closed for lighting the out ringing lamp 266 which is traced from battery through lamp 266, lower contacts of relay 238, over conductor 262, lower inner breakV contacts of relay 246, lower contacts of key 236 to ground on the lower inner make contacts of relay 223. Another circuit is also now closed for energizing the winding of selector rotary magnet 254. This is traced from battery through the winding of magnet Y254, lowermost back contacts of relay 24|, lower contacts of key 249, front contacts of relay 2li), upper, inner, front contacts of relay 238, lower, inner back contacts of relay 258, upper, inner, back contacts of relay 246, lower contacts of key 236 to ground on the lower inner contacts of relay 223. 'Ihe ringaol-salty;r

ing condition is maintained on the line while the selector is. advanced under control of the interrupter circuit I and the relay 2I0. Ground is connected to a terminal of the bank associated with selectorhrush256, by manually operating the grounded brush 263 of a dial switch. The particular terminal on which brush 263 stands determines the length of the outgoing ringing signal as will now be explained. When the selected bank terminal is reached by brush 256` relay 246 operates in a circuit traceable from ground on brush 263 through the selected contact of the associated dial switch over the connecting strap, to the selected bank terminal, through brush 256, lowermost break contacts of relays 239 and 256, winding of relay 246 to battery 240 through the uppermost back contacts of relay 24l. Relay 246 in. operating locks through its upper, inner front contacts to holding ground on conductor 26.4, transfers the holding circuit for relay 232 which was hereinbefore traced from holding ground on conductor 264, to off-normal ground onthe lower contacts of spring combination 232. Relay 246 in operating also causes the ionic tube interruptor circuit I to function at a slowv rate by removing the short circuit around .the resistance 265, which is normally maintained through the lowermost contacts of relay 246, thereby increasing the resistance in the condenser timing circuit. Three hundred thousandohms, in practice, hasbeen found to be a convenient value for the resistance 265. Relay 246 also opens, at its upper, innermost back contacts the operating circuit for the stepping magnet 254, which was hereinbefore traced, thereby stopping the further motion of the selector switch, it also energizes the release magnet 259 through a circuit traced from battery through the winding of magnet 259, upper front contacts of off-normal springs 232, upper middle contacts of relay 246, contacts 26| of relay 238, lower inner make contacts of relay 245 to off-normal ground on conductor 261. When the selector switch restores, the olf-normal springs 232 restore to normal, opening the locking circuit of relay 238, which releases, disconnects with its upper middle contacts battery 246 `from the toll line and extinguishes the out-ringing lamp 266.

With relay 246 operated and relays 239', 238 andV 24| normal, the circuit measures an interval of time Isuiiiciently long to receive a return ring from. theftest circuit at the distant end of the toll line. The operating circuit for the step magnet is completed from ground through the upper'middle contacts of relay 239, uppermost f front contacts of relay 246, lower inner back contacts of relay 24i, upper inner back contact of relay 236, front Contacts of relay 2l0, lower break contacts of key 249, lowermost break contacts of relay 24E and windingl of magnet 254r to battery. The selector timing switch is thus caused to again advance its

brushes

255 and 256` under control of the interruptor circuit I andrelay 2 l D untilA one of two conditions is satised--either (a) an incoming ringing signal is received before selector timing brushes 2.55- and 256 reach theY tenth or last terminals or (o)` the signal is notv received before saidtenth terminals are reached. If the ringing signal is not received, ground from the upper innermost front contacts of relay 246, upon which this relay previously locked is passed through the lowermost back contacts of relay 239 to selector brush. 256, through the associated tenth terminal and the winding of blocking relay 235 to battery. Relay 23.5 in operating closes a locking circuit for itself which is traced from battery through its winding and lower front contacts, upper contacts` of release key 236, to ground on contacts 234 of jack 209. In operating it also lights lamp 268 and opens the circuit of relay 223, which releases. Relay 2.23 in releasing disconnects ground 224 and thereby o-pens the anode circuit of the ionic tubes of interrupter circuit I, which thereby stops func.- tioning. The operating circuit of relay ZID being likewise opened, this relay stops operating and the circuit of the rotary stepping magnet 254 is accordingly opened. The release of relay 223 also opens the :previously traced locking circuit for relay 246, .whichreleases 'The release of relay 223 also energizes the winding of release magnet 259 in, a circuit from battery, through the Winding of magnet 259, upper contacts of offnormal springs 232, uppermost contacts of relay 223 to ground onthe lower contacts of springs 232. The timing selector switch is accordingly restored to normal and the circuit for the magnet 259, before traced, is opened when the oli-normal springs 232 are released. Lamp 268 remains lighted until the tester restoresthe circuit to normal by operating the release key 236.

Assume, however, that the incoming ringing signal is received beforeV the timing selector circuit reachesv terminal i6. 'Under' this condition, marginal sleeve relay 243 operates in response to the incoming signal, asbefore described, in turn operating relay 239; The operation of relay 239 disconnects ground, a-t its upper middle contacts, `from the circuit of rotary stepping magnet 254'and energizes release magnet 259 from groundV on the upper innermost make contacts of relay 246, through lower outer operated front contacts of relay239,upper operated ofi-normal springs 232 and winding of magnet 259 to battery. When the timing selector switch and springs 232v are restored to normal a circuit is closed for operating relay 258 which is traced from battery through the winding of relay 258, back contacts of springs 232, lower outer operated front contacts of relay 239 to the locking ground on the upper innermostfront contacts of relay 246. Relay 258, in operating, opens the locking circuit ofrelay 246 which releases; Relay 246, in releasing, disconnects with its upper innermost front contacts, the grounded conductor264 from .the winding of relay 256l which releases. With

relays

256 and 246 released and the selector timing switch restored to normal, the test circuit functions as described for the initial incoming ring.

Itis sometimes desirable to locate the test box at a distance from the test and control board and the operation of the invention will now be described for this condition.

Before the test is started, jack lill is patched to jack 201., theV tip, ring and sleeve conductors of which are wired to the corresponding conductorsv ofv the jack'296 of the distant test box. The toll cord |01, shown in an abbreviated form, is plugged into jack 202, the tip conductor of which is wired to-the lower spring of start key 23?, and the ysleeve conductor to a multiple connection with lamp 268 through a resistance 269; Also, before starting the test, brushl 263 of the dial switch should be moved to its normal position to avoid interference and jack i 62 should be patched to one of the

jacks

263, 254 or 255. The tipi conductors of these jacks `are wired, as shown in the drawings, to terminals 4, 6 and 8, respectively, of the selector switch bank associated with the brush 256, the order of numbering being that indicated by the direction of the arrow. It is to be understood, however, that these jacks may be wired to other terminals of the switch if desired. The sleeve conductors of jacks are multipled and are wired in multiple with the local contacts 234 of jack 200 of the test box. To provide battery for the operation of the test box, jacks 20'1 and 209 should be patched to conveniently located battery supply jacks, not shown, which are equivalent to jacks |03 and |04.

Let it be assumed, for this descrip-tion, that jack |02 is patched to jack 205. With this arrangement, ground on the sleeve of jack |02 is connected throu-gh to terminal 6 of the selector switch and corresponds to the connection of ground by dial switch brush 263, as was described in connection with the use of the test box when located directly at the test and control board. In other words, the length of the outgoing ringing signal is determined, in the case of remote operation of the test box, by the

particular jack

203, 204 or 205 which is patched to jack |02.

When jack |02 is patched to jack 205, a circuit is closed for operating relay 223 which can be traced from battery, through the winding of relay 223, lower back contacts of relay 235, upper break contacts of key 236, ring conductors of jack 205, cord |06 and jack |02 to ground.V Relay 223, in operating, functions as before described when it operated in response to the closing of springs 234 of jack 200. ToV start the test, ringing key |12 of the cord |01 is operated, thereby connecting battery through resistance |13 over the tip conductor of cord |01 and jack 202 to the upper winding of relay 238. This relay now operates, connecting battery 240 to the tip conductor of the toll line and from this point on the description hereinbefore given in connection with the operation of the test box, when located at the test and control board is applicable. It is to be understood, of course, due to the remote location of the test box, the indications of the lamps in the test box are not available with this method of testing. No provision is made for giving at the switchboard, indications of the outgoing ringing, but the supervisory lamp- |14 of toll cord |01 plugged into jack 202 is energized for an incoming ringing signal, in multiple with lamp 268 through resistance 269. Lamp |14 also lights for a timed out condition from ground on the upper front contacts of blocking relay 235, when this relay operates.

The test set may be stopped at any time by removing plug ||4 from jack 200', when the test set is located at the switchboard, or by disconnecting

jack

203, 204 or 205 from jack |02, when the test box is at a distance from the switchboard. This removes the operating ground for relay 223 which releases and thereby stops the functioning of

tubes

2 and 2 I2. The release of relay 223 also closes a circuit from -ground on lower off-normal springs 232, through its upper outer break contacts and upper front contacts of springs 232 to battery, through the release winding 259 of the associated selector switch, which releases, if it should be off normal at this time. The release of relay 223 also causesl the release of all operated relays.

The speed of the interrupter circuit I may be varied by means of the variable resistance 23|. This resistance with the

condensers

230 and 233 may be designed so that theinterrupter functions at the rate of five, four, three, etc., pulses per second. A convenient means of checking the pulsing rate is provided by the key 249 and register 241. The operation of key 249 closes a circuit from -ground on the upper outer contacts of key 249 through back contacts of relay 2|0, upper inner-front contacts of key 249 and winding-of register 241 to battery. Register 241 now automatically counts the operations of relay 2 |0`. By noting the number of operations in-thirty or sixty seconds, or some other convenient period of time, and adjusting the variable resistance 23| as necessary, the rate of pulsing may be adjusted quite accurately.

What is claimed is:

l. In a signal timing circuit, a line, a source of signaling current, means for connecting said source to one end of the line, and a signal receiver connected to the other end of the line, said receiver comprising a progressive indicating means, switching means for controlling the progress of said indicating means, timing means for controlling said switching means at a predetermined rate, and means responsive to the received signal for causing said timing means to control said switching means and to cause said switching means to advance said indicating means.

2. In a signal timing circuit, a line, a source of signaling current, means for connecting said source to one end of the line for a certain interval of time and a signal receiving arrangement connected to the other end of the line, said arrangement comprising a plurality of visual sig- Y nal devices, switching means for controlling the display of said devices in successive order, timing means for controlling said switching means to successively display said signals at a predetermined rate, and means responsive to the received signal for causing the timing means to control the switching means and for causing the switching means to control the signal device.

3. In a signal timing arrangementQa line, a source of signaling current at each end of the line, means for connecting one of said sources to one end of the line and signaling receiving and transmitting apparatus connected to the other end of the line, said apparatus comprising progressive indicating means, switching means for controlling the progress of said indicating means, timing means for controlling said switching means at a predetermined rate, means responsive during the continuance of a received signal for causing said timing means to control said switching means and to cause said switching means to advance said indicating means,

and means operated upon cessation of said received signal for connecting the respective source of signaling current to the line and for causing said switching and timing means to hold the connecting means operated a predetermined interval of time.

4. In a signal timing arrangement, a line, a source of signaling current and a signal timing test at each end of the line, said test set comprising a progressive switching mechanism, a progressive visual signal indicating device controlled by said switching mechanism, an interrupter for advancing said switching mechanism at a predetermined rate, means for connecting each set with the line, ringing means associated with each set for connecting the associated current source to the line and for connecting said interrupter to said switching mechanism, manual means for initially operating one of said ringing means, adjustable means responsive to the switching mechanism advancing to a predetermined position for arresting said switching mechanism and disconnecting the interrupter therefrom, means associated with each set responsive to a signal received over the line to connect the interrupter to advance the switching mechanism and thereby advance the indicating means accordingly during the continuance of said signal, and means operated upon the cessation of said received signal to automatically operate said ringing means to connect the associated current source to the line under control of said switching means and interrupter.

5. In a signaling timing system, a line, a source of signal current at each end thereof, means for connecting the source at one end to the line for a predetermined interval, means at the other end for indicating the length of the signal received and thereafter automatically connecting the source thereat to the line for a predetermined interval, and means at the rst end for indi- A eating the length of said second signal and thereafter again connecting the source thereat to the line for a third predetermined interval.

6. The method of determining the ringing margin of a telephone line which consists in transmitting a ringing signal of predetermined duration over the line, indicating the duration of the received signal at the other end in a progressive device and thereafter automatically transmitting ringing signals of said rst predetermined duration back and forth over said line alternately and receiving them in progressive devices as long as the signals received at either end actuate the progressive devices thereat to indicate a signal of predetermined duration.

7. The method of determining the ringing margin of a telephone line which consists in transmitting a ringing signal of predetermined duration over the line, indicating the duration of the received signal in a visual signal device at the other end of the line, automatically trans mitting a return signal of predetermined duration back over the line responsive to cessation of said received signal and the indication of a signal of predetermined duration in said device,

indicating the duration of the return signal received at the rst end of the line in a visual signaling device, automatically transmitting a return signal of vpredetermined duration over the line to the second end of the line responsive to cessation of the signal received and a predetermined indication of its duration, and automatically continuing the operation as long as signals of a predetermined duration are indicated at each end of the line.

8. In a timing circuit, two gas-filled discharge devices each comprising a cathode, an anode and a control electrode, a connection including a condenser between the anode of the rst one of said devices and the control electrode of the second device, another connection including another condenservbetween the control electrode of the first device and the anode of the second device, a high resistance connection between the respective control electrodes and an electroresponsive device in the anode circuit of one of the devices.

9. In a`timing circuit, a pair of gas-filled discharge tubes each comprising a hot cathode, an anode and a grid electrode, a condenser connected between the anode of one tube and the grid of the second tube, another condenser connected between the grid of the rst tube and the anode of the second tube, a high resistance connected between the grids of the two tubes, and

a relay in the output'circuit of one of said tubes.

10. In a timing circuit, a pair of gas-llcd discharge tubes each comprising an anode, a cathode and a grid electrode, a condenser connected between the anode of one tube and the grid of the other tube, another condenser connected between the remaining anode and grid, a high resistance connected between the grids of the two tubes, a relay in the output circuit of one of said tubes, and means for varying said high resistance.

EARL S. GIBSON. ARNOLD A. HANSEN. JOHN B. WORTH.