Patent GB-488430-A (GB)
Title: Improvements in or relating to telephone systems
IPC: H04Q1/36
Filed: 1937-01-06
Abstract: 488,430. Automatic exchange systems. AUTOMATIC TELEPHONE & ELECTRIC CO., Ltd., McCLEW, J. W., and WILLIAMS, A. H. Jan. 6, 1937, No. 435. [Class 40 (iv)] A mechanical repeater for regenerating impulses such as that described in Specification 458,095, is re-operated, after the connection has been established, to control metering in accordance with the duration of the call. The impulse responsive member of the repeater is, on reply of the called party when metering first occurs, stepped by timed impulses until the end of a 3-minute period approaches whereupon off-normal springs are operated and the calling party is warned. If he does not release the connection or, in case of coinbox calls, pay an additional fee, the call is metered again or the coin-box connection broken down. Outgoing call from ordinary line. The repeater is seized over - + P whereupon A, B, IP, BR, AL and BB pull up, and the junction is looped over D, I and the impulse springs IMP. The impulses are repeated to relay C and magnet RM which steps disc R of the mechanical repeater S, P. R, magnet MM being operated by C to withdraw the pinoperating lever of disc R. Off-normal contacts N1 close. When C falls back at the end of the train, MM releases and causes the lever to push the selected pin on disc P into the path of a pin on disc S. Relay ON pulls up and locks for the remainder of impulse repetition and operates relay AP over the contact between the previously protruded pin on disc P and the pin on disc S. Relay ON also connects springs IMP directly across the loop. Relay IP releases slowly (providing the interdigital pause after subsequent digits) and magnet SM is operated and then released by interaction with AP to release the sending disc S as described in the above-mentioned Specification. Relay IP re-operates on the relapse of AP. When all the digits have been re-transmitted, disc S catches up with disc R and off-normal contacts N1 release ON to re-insert D, I in the loop. When D operates on reply of the called party, DD, DR follow and start the control of delayed metering relays DA, DB by pulses over S and Z. During the operation of both DA and DB, J is operated by one or more pulses over MP in accordance with the tariff for the junction and connects booster battery impulses to wire P. On termination of the Z pulse DA relapses but DB holds to connect stepping magnet RM of the impulse regenerator to lead 12 which is grounded every 4¢ sec. During these impulses MM, initially operated by C, is held over YB but ON nevertheless pulls up since DR is operated. Towards the end of the 3 minute period when R has been rotated 37 steps, the off-normal springs N1 are opened and T pulls up in series with AP and ON which are therebv held. Stepping magnet RM is disconnected from the pulse lead, magnet MM is released to operate a pin on disc P, and two-step relay CD is connected to 12-sec. pulse lead 14. When CD operates fully on termination of the next pulse, the pulse lead 14 is connected to twostep rely CO and SM is operated to release the sending disc as previously described, the impulse springs IMP being however ineffective due to the operation of CD which sends a warning signal from lead 11 to the calling party. If the conversation is not terminated in the grace period of 12 sec. before the operation of CO repeat metering takes place at once or after a further period of 12 sec. If terminals 15, 17 are strapped, CO shunts DB immediately whereas if 15, 18 are strapped, this does not occur until the next pulse on lead 14. If terminals 17, 16 are strapped repeated metering occurs only on coin-box calls (see later). The release of DB is followed by that of CD, CO and repeat metering is initiated by the S and Z pulses as before, magnet RM also being re-connected by the re-operation of DB to pulse lead 12 to time the next 3 minute period. Release. Relays A and B fall back, C pulling up during the slow period of B. Relay B opens the forward loop and removes holding ground from the preceding switches to release them, but BR released by B re-connects the ground to guard the repeater until the regenerator has been restored (BB released). Assuming that the regenerator has commenced the timing of a fresh conversation period, MM is released on the relapse of C and DR to operate a pin to provide a homing position to which S proceeds due to the operation of SM. When off-normal contacts N1 open, ON and BB fall back to release the repeater. If the calling party hangs up during the grace period, the regenerator will have been released already. Premature release. If this occurs before sending is completed, any digits stored are sent to an open circuit without interdigital pauses since IP cannot be operated after the release of B. Call from coin-box. The repeater is seized over the same leads - + P as before but the selector giving access thereto puts a battery pulse on the P lead to operate TE which is followed and locked by CB. Operations proceed as before up to the giving of the warning signal towards the end of the 3-minute period, but in the present case, TG is operated over lead 11 and the secondary of the signal transformer, and locks over its upper winding since TE has been released by DA. Relay A is now dependent on DB which will be released at the end of the grace period so that the connection breaks down unless further coins are inserted. If this is done, a further battery pulse re-operates TE and on operation of CO at the end of the grace period TG falls back and maintains A operated. The effects of certain arrangements of straps between 15 .. 17 have previously been referred to but if 15 and 16 are strapped to 17, 18 respectively and a rest contact of CB is included in the lead to 17, both ordinary and coin-box calls are metered or charged according to duration but the coinbox party has an extra period of grace. Repeater at tandem exchange. The repeater is seized by an incoming selector over -+P2 in which case J operates, locks up and opens the initial circuit of DA thereby preventing the timing apparatus from functioning. Merging numerically separated calls. The repeater may also be seized over -1, +1 in which case LD operates in series with A and is held over its right-hand winding, the left-hand winding being shunted by BB to preserve line balance. LD grounds both legs of the outgoing junction to operate a differential wiperswitching relay at the incoming selector and is released when C pulls up. Fault alarm arrangements. If the regenerator fails to send, ON remains operated, holds BB to guard the repeater and lights lamp LP over delayed alarm lead 13. If the regenerator does not respond to impulses or fails to home after a timing period (ON released), AL holds with similar results.