Patent GB-265251-A (GB)
Title: Improvements in telephone systems
IPC: H04Q1/20
Filed: 1925-08-29
Abstract: 265,251. Standard Telephones & Cables, Ltd., (formerly Western Electric Co., Ltd.), (Polinkowsky, L., and Hatton, W.). Aug. 29, 1925. Automatic exchange systems. - The various functions of automatic exchange equipment are tested in a series of cycles which follow one another automatically until a complete test has been effected or a fault is encountered. In thelatter case the testing operations cease and an alarm is given. Means is provided by which a reduced number of cycles or only a single cycle may be effected when desired, e.g. for a morning test, whilst the test of a particular function may be repeated indefinitely if desired. As applied to a final selector, a complete test comprises at least three cycles in each of which the final selector goes through all the stages of a complete call, in the first cycle under idle conditions of the called line, in the second under busy conditions and in the third under idle conditions again, the first two cycles testing the selector impulsing contacts for correct openings and closures whilst in the third cycle the contacts. are tested for vibration or intermittent contact. Similar cycles under alternate idle and busy conditions may follow one another indefinitely until stopped by an attendant or the presence of a fault. The abbreviated or morning test comprises the first cycle only. In final selectors having access to private branch exchanges, the P.B.X. hunting operation is also tested. As anplied to register-controllers, a complete test comprises eight cycles during the first five of which different four-digit numbers are transmitted to the register-controller and corresponding numbers of reverting impulses are sent over the outstepping circuit. The remaining three cycles test the operation of the register-controller under conditions of special call, premature release, and permanent loop, respectively. The abbreviated or morning test comprises the first five cycles only. Provision is also made for a manual test of the register-controller. Testing final selector; abbreviated or morning test. The leads 1 - - 8 outgoing from the test set, Fig. 1, (21673/25), are multipled to the test keys TK of final selectors such as that shown in Fig. 1<A>, the leads 1 - - 4 being associated with the incoming circuits as shown whilst leads 5 - - 7 are associated with the twentieth terminal in the tenth level of the selector. For the aibbreviated test, key FK of the test set and key TK of the particular final selector are thrown. A circuit is then completed over lead 4, timing-device TD in its normal position, and cam Q for relay Rdr which starts up the magnet TA of the timing-device and connects relay Lr across wires 1 and 2 in series with relay Flr of the final selector. The latter drives sequence switch Ra, Fig. 1<A>, to its 2nd position, whilst relay Lr also operates and connects the left-hand winding of relay Swr over lead 3 to the incoming test wire. If this wire is continuous and of correct resistance, relay Swr operates and energizes relay Frr which drives the test sequence switch R to its 2nd position. Relay Flr now locks to the fundamental circuit over leads 1, 2 in series with relay Sr which energizes relay Scr9 of the counting chain. The trip spindle rotates and at each step an impulse is sent back from interrupter INT2 to relay Sr. After ten steps, relay Tcr opens the fundamental circuit, switch Ra moves to position 4 and switch R to position 3. If the incoming test conductor is still in order, relays Swr, Frr again operate and move switch R to position 4 and during this movement a momentary release of relay Flr causes switch Ra to move to position 5“ in which the brush carriage rotates. Relay Sr, operating in the fundamental circuit, energizes counting relay Scr10 and after eleven steps the operation of relay Tcr10 removes a short-circuit from relay Hr which operates in series with relay Gr and opens the locking circuits of relays ScrO, Tcr0, - - Scr8, Tcr8. The brush carriage therefore takes a further nine steps to the twentieth terminals when relay Tcr opens the fundamental circuit, switch R moves to position 5 and switch Flr to position 11. During the setting operation the counting relays and the stepping relay Sr are connected in series with resistance so that they operate more slowly than normal register-controller relays and thus test whether the openings of the final selector interrupters are of correct duration. The disconnection of battery at cam G, Fig. 1<A>, causes relays Swr, Frr to release and drive switch R to position 6. If the selector ha.s been correctly set, the test relay Ftr operates in position 6“ of switch Ra in series with relay Tbr over lead 7, and relay Tbr completes a locking circuit for relay Ftr over cam D, Fig. 1 (21673/25), relay Swr, lead 3. and cams C, J, Fig. 1<A>. If the selector has not been correctly set relay Ftr does not energize and the switch is restored to normal in position 11 of switch Ra so that the subscriber on whose lines the selector is incorrectly resting will not be rung. If correctly set, relay Flr operates over cam E in position 10# and locks in position 11 over cam K and wire 3 and moves switch Ra to position 12, further movement to position 14 being effected by interrupters W2, W3. Ringing-current over interrupter W1 is now connected over relay Rgr, lead 6, relay Tjr. lead 5 and cam H, relay Tjr being combined with condenser and resistance to simulate two subscribers' sets in parallel. The ring-cut-off relay Rgr should not energize at this time but relay Tjr responds to the ringing-current and operates relays Mor, Frr. At the next break in the ringing-current, the release of relay Mor drives switch R to position 7, and similarly at the succeeding break, switch R moves to position 8 in which earth is connected over lead 6 and relay Rgr should operate and release relay Flr to drive switch Ra to position 15. The con. tinuity of the talking circuit is now tested by the connection of relay Sr over cams L, K to leads 1, 2 and thence over cams M, N. Fig. 1<A>, brushes A, B, leads 5, 6 to battery and earth. If this circuit is continuous, relay Sr operates to move switch R to position 9 in which relay Sr is connected over cams I, J to leads 5, 6, and earth is disconnected from lead 3 so that relay Flr de-energizes and moves switch Ra to position 16. Relay Flr is now operated again and holds over cam N, leads 5, 6 and relay Sr. The latter energizes relay Frr to move switch R to position 11. Whilst passing positions 10-10“ the condtiion of breakdown from a toll connection is tested by application of earth over cams F, E and lead 7 to release relav Ftr. This causes switch Ra to move out of position 16 and restoration is completed in known manner. The release of relay Sr releases also relay Frr and a circuit is then completed over cams T, V and key FK for lamp RAL which indicates the successful completion of the test. The restoration of key TK releases relay Rdr which completes a restoring circuit for switch R. Complete test of final selector. In this case key FK is normal and key AK operated. The first cycle takes place in the manner described in the preceding paragraph but the release of relays Sr, Frr in the 11th position of switch R completes a circuit over cam V and the back contact of key FK for moving switch R into position 12 in wich it waits until the selector is fully restored. Relay Sr then energizes over the fundamental circuit but this time in series with a lower resistance so that it is quicker in operation and slower in releasing and tests that the selector interrupters give correct closures. The final selector is then set in a similar manner to that in the first cycle to the 20th terminal on the 10th level after which switch R moves to position 15. On this occasion the selected line is marked busy by an earthed tone-coil connection over cam U to lead 7. Relav Ftr should not operate, but relay Tbr operates and completes a circuit for relay Lkr which locks over cam S and earths the third wire 3. When the final selector leaves position 5“ battery is disconnected at cam G, Fig. 1<A>, so that relays Sur- Frr release and switch R moves to position 16. Relay Frr now operates again over cam C and moves switch R to position 17 in which a relay Dcr which was energized between positions 16 and 17 is short-circuited. Upon the release of relay Dcr which takes place slowly, switch R moves to position 18 in a circuit over cam H. If the final selector correctly makes the busy test, relay Tbr will de-energize as soon as switch Ra leaves position 6“ relay Lkr releases in position 18 of switch R, and the consequent release of relay Frr closes a circuit over cams T, V for restoring switch R to position 1. If, however. the test relay Ftr energizes, relays Tbr will lock as in the first cycle over a front contact of relay Ftr and wire 3, and switch R will remain in position 18. The transmission of busy tone from coil BTC in position 9 of switch Ra may be tested by means of a telephone plugged into jack TJ in the testing set. In position 17 of switch R. relays Ir, Ir1 operate and lock over cam P, short-circuiting the resistances in series with the counting relays so that in the third and fourth cycles which proceed in a similar manner the counting relays operate quickly and a test is made for vibration on the final-selector interrupters which would result in an incorrect operation of the counting chain. During the fourth cycle, relay Br operates to release relays Ir, Ir1. Testing cycles thus continue indefinitely, with the test line alternately idle and busy, until stopped by the operator or by the discovery of a fault. In the latter case, the timing-device TD after an interval lights lamp RAL and operates relay Prr to sound an audible alarm. A meter RTM registers the total number of cycles performed. Testing P.B.X. final selectors. For this purpose, lead 8 from Fig. 1 (21673/25)