Patent GB-808375-A (GB)
Title: Improvements in or relating to register-connectors for use in telephone systems
Inventor: PEARCE JAMES GORDON
IPC: H04Q3/00
Filed: 1955-08-25
Abstract: 808,375. Automatic exchange systems. AUTOMATIC TELEPHONE & ELECTRIC CO. Ltd. Aug. 7, 1956 [Aug. 25, 1955], No. 24430/55. Class 40 (4). In a register-connector in which a connection between a transmission relay set and a register is established by the firing of two gas discharge tubes, each tube also serves for the transmission of two distinctive signals each conveyed by a different level of current flow in the tube. In the arrangement described each incoming junction relay set IRS has access to a number of common registers REG over pairs of tubes RCA, RCB, there being one such pair for each possible relay set-register connection. Tubes MK, SZ, SZA, MKA, RO and SO constitute that stage of a high-speed hunting circuit, embracing all the relay sets, which forms part of the relay set IRS; and tubes RM, RS, RSS, RMA, RR and SR that stage of a similar circuit, embracing all the registers, forming part of the register REG. On seizure of the incoming relay set shown, operation of the A relay (not shown) connects + H.T. to the common start lead ST of the register-connector control circuit (not shown), which in due course connects H.T. to leads CHT and CHTB in all incoming relay sets and all registers. Relay A also primes the marking tube MK in the seized relay set and causes tube BA to fire (with delay). The positive pulse from the cathode of BA fires the permanently primed tube STO, whereupon relay ST pulls up. With H.T. connected to CHTB, the primed tube MK fires in all seized relay sets due to the conduction of common tube MKF, whereupon MKA fires, SZ is primed and RO backed off. Idle registers have relay BB (not shown) imoperated and hence only in them is CHT connected to the anode of the marking tube RM, so that when H.T. is connected to CHT in all registers the marking tube RM fires in idle registers only, whereupon RS is primed, RMA fired, and RR backed off. Selection of idle register.-The control circuit then applies a positive potential to a lead of the first stage of the register hunting circuit corresponding to lead 20. If none of the registers preceding that shown is idle, the tube SR in the preceding stage PRHS fires and applies a positive pulse to the triggers of RS and RR. If the register shown is idle, RS fires followed by RSS. A positive potential is thus applied over common lead RHF of the control circuit to indicate that the register hunt is completed, and over a common lead to the triggers of all tubes RCA, RCB giving access to the particular register. Operation of hunter when register busy.-The firing of tube SR in stage PRHS fires RR (instead of RS) followed by SR of the stage shown, which applies a positive pulse to the triggers of RS and RR of the next stage SRHS. Selection of seized relay set and connection thereof to chosen register.-In response to the signal over lead RHF the control circuit applies positive potential to a lead of the first stage of the relay set hunting circuit, corresponding to lead 10, and if none of the relay sets preceding that shown has been seized, tube SO in the preceding stage PHS fires and pulses the triggers of SZ and RO. Tube SZ, primed by MK, fires thus applying positive potential to common lead THF to indicate to the control circuit that the hunt has been effective, firing CNO to bring up relay CN, and firing SZA which pulses the triggers of all tubes RCA and RCB associated with the particular relay set. Of these tubes that pair giving access to the chosen register is already primed and it fires, thus connecting the relay set and the chosen register. Operation of hunter stage of unseized relay set.- In such a stage, MK and MKA are not fired, so that when tube SO of stage PHS fires, tube RO fires (instead of SZ), SO follows and pulses the triggers of tubes SZ and RO of the next stage, NHS. Release of register-connector control circuit.- This is effected by the potential applied to lead THF, and H.T. is thereupon disconnected from CHT and CHTB to douse all fired tubes in the hunting circuits. Signalling over the register-connector tube RCA.-The operation of relay ON douses tube BA, removes the priming potential from MK and transfers the control of BO from contacts of A to contacts of HDB. In the normal condition of the register tubes VA and VB are non-conducting, and VC is conducting, other than during the short period immediately after the release of the exchange controller (not shown) when H.T. is disconnected by the latter from leads EHTA. Tube OT is thus normally insensitive to signals applied to its trigger. When the incoming relay set IRS has been connected to the register, the current flow in tube RCA is determined by the state of relay A in IRS, and that of relay SW (not shown) in the incoming selector IS, and in turn determines the state of tubes VA and VB. With SW down and A up, VA and VB both conduct; with both relays up, VA alone conducts; and with A down (SW in either condition), neither tube conducts. Consequently, regardless of the condition of the incoming selector, dialled impulses are repeated by relay A to relay AA (in the anode circuit of VA), which effects their storage. After reception of all the digits VB will be conductive provided the selector IS is free, thus cutting-off VC and enabling OT, and the reception of a pulse on lead SDS from the storage elements (not shown) fires STT which is followed by STA, OT, CSS and by SEA and SEB which have their anode loads connected over leads EA and EB to the exchange controller. The latter, if idle, is then connected to the calling register and all information necessary for the setting-up of the call is transferred to the controller. Incoming selector busy.-Tubes STT and STA fire as above but only the minor gap of OT is fired, until IS becomes available, whereupon VC is cut-off and the main gap of OT conducts. Exchange controller busy.-Assuming IS to be idle, SEA and SEB fire as above but without effect, and when the exchange controller duly releases they are doused and the momentary disconnection of H.T. from EHTA douses VC, STA, OT and CSS. On reconnection of EHTA, STA again fires and if VC remains non-conductive, OT is fired and a new demand is made on the controller. Signalling over tube RCB.-A different " class-of-service " lead, such as RBA, is provided for each class of service to be afforded to different incoming relay sets by the register, and the cathode of each tube RCB is connected to the appropriate one of these leads. Assuming this to be RBA, the potential produced at the cathode of RCB primes tubes CA, CB associated with that lead. On seizure of the exchange controller, H.T. is connected to leads HT(EC) and a pulse is then applied to lead TP in the individual register, whereupon CA, CB and LMO fire and relay LM pulls up. The cathode potentials of CA and CB are applied over leads LA and LB to give a two-out-of-five indication of the class of service to the exchange controller. Operation of LM douses STT to prevent a second demand on the controller, and short-circuits the cathode load of RCB to provide an abrupt rise in current through the tube and thus to fire HD in the incoming relay set IRS. Relay HDA operates applying positive potential to lead MF to initiate the forward marking of all idle paths through the exchange accessible to IRS, and bringing up HDB which fires BO after a delay sufficient for the setting up of the call to be completed. Relay B then pulls up, completes connections (not shown) between the incoming junction and IRS, and douses RCA and RCB, whereupon VA is cut-off, AA restores and the register is released. Premature dialling.-If dialling occurs before a register has been connected up, CN will be down and the first release of A causes firing of BO. The operation of B then disconnects lead ST and the anodes of all tubes RCA, RCB associated with IRS, and the hunting circuits are reset to normal. Under these conditions additional contacts (not shown) of relay B cause busy tone to be reverted to the caller.