Patent GB-366594-A (GB)
Title: Improvements in or relating to telephone systems
IPC: H04Q3/42
Filed: 1930-11-07
Abstract: 366,594. Automatic exchange systems. AUTOMATIC TELEPHONE MANUFACTURING CO., Ltd., Strowger Works, BELAS, F. T., 24, Stanley Street, both in Liverpool, and BAKER, G. T., Blackbrook, Caerphilly, Glamorgan. Nov. 7, 1930, No. 33579. [Class 40 (iv).] In a numerical switch having a transmission bridge, the outgoing speaking conductors are connected, prior to the setting of succeeding switches, to provide a battery feed circuit (local call) or a loop circuit (call to another exchange or manual board) under control of auxiliary apparatus common to a group of such switches. The invention is described in connection with a first code selector, and the normal battery feed is replaced by a loop under the control of a relay BA which is operated or not in accordance with the condition of a group of auxiliary relays MA .. MD in the A-digit switch. These relays are set by a preliminary train of impulses from the register-translator, and also serve to determine the number of metering impulses and prevent metering of a call to manual. Relay BA provides an additional guard for the junction. Re-routing facilities are provided, but the first re-routing digit passes to the first code selector and not to the auxiliary relay group. Hunting of the first code selectors is controlled by a common stepping relay in the A-digit switch. An operator may recall a calling party by connecting up ringing current which operates a relay, shunted by a rectifier, to connect ringing current at the first code selector. The registertranslator (not shown) is similar to that described in Specification 361,849 but grounds a normally battery-connected re-routing conductor when re-routing is to take place, and for forced release, disconnects a normally grounded forced release conductor in addition to grounding the re-routing conductor. Specifications 366,469 and 366,593 also are referred to. Seizure and preparation of A-digit switch. Relays L, B in the first code selector complete a circuit for MG over K (upper) which remains inert, and MG interacts with ADM to step ADF until wiper 1a finds low resistance battery over resistance 1YB and relay 1B in parallel so that MG is short-circuited and K operates over both windings; locks up, disconnects MG and switches through to the wipers of ADF. Relay B holds over the homing wiper 2a. To prevent dual. connections the K relays of first code selectors are adjusted so that two will not hold in parallel. In the A-digit switch, relay 1B operates, locks over wiper 1a and energizes C (left-hand winding) and CA (lower). Relay A also pulls up, and dialling tone is sent out over 1N3, QD, NR3, QD1. Setting the A-digit switch and associated auxiliary relay group. The first digit is repeated by relays L, A to relay C and vertical magnet 1VM in series, the original circuit for C being opened at 1N1 at the first step. At the end of the digit C relapses and operates rotary magnet 1RM which interacts with G (right-hand winding) operating in series with HC (lower) which remains inert. When an idle register-translator is found, low resistance battery over 2P short-circuits G and operates HC over both windings in series. Contact hc1 operates first to connect ground normally on the forced release wire of the register-translator over FR, ca2, 2I, D, ca5 to hold A during the switching operations of HC, this ground being subsequently replaced by one over 3+. Relay HC also transfers A from the first code selector to wiper PU, busies the register-translator by connecting up ground from lb3 over the upper low resistance winding of HC, and reoperates C. The register-translator, after reception of the C-digit, and if the call is not a local one, sends one, two or three impulses to A dependent on the zone of the wanted exchange, and a fourth pulse for a purpose to be described later, relays MA .. MD being operated in various combinations described in subsequent paragraphs. At the end of the metering control impulses, the register-translator connects ground to RR to operate KR and hold CA. Relay KR operates J and these relays prepare circuits for setting the first code selector. First code selector. The first routing digit is repeated by A to vertical magnet VM and the subsequent removal of ground from RR releases CA and opens the circuit of KR (lower), but ground over ca3, ga2, KR (upper), holds KR and operates the rotary magnet RM which interacts with GA, Fig. 4. If both lines test busy, ground on P operates GA (left-hand winding) which releases RM at ga2, connects its right-hand winding to IP without effect, and is released by RM. If P finds an idle outlet, HA operates in series with GA which remains inert, opens the circuit of HB, grounds P and switches through to wipers 1. If 1P finds an idle outlet, GA operates over P and locks over its right-hand winding in series with HB which disconnects HA, grounds 1P and switches through to wipers 2. If both P and 1P find idle outlets, that over P is selected since GA remains inert and HB is not connected up. At the end of rotary movement KR falls back and transfers the holding circuit of HA or HB to wiper RR which is connected to battery in the register-translator. CA does not operate in this circuit. Completion of connection. The registertranslator sends out the remaining digits and then disconnects battery from 2P so that HC falls back, transfers the holding circuit for switching relay HA or HB to battery over resistance YD, and replaces the loop at the translator by a loop over D, 2I in the A-digit switch to hold the switch train. The wanted party is rung from the connector, and ring-back signal passes to the called party over wiper 1 - of the first code selector and wipers 6a, 4a of switch ADF. When the called party replies, reversal of current flow operates D which releases C. Relay HR in the first code selector now pulls up, completes the speaking path, locks HA or HB, and prepares a booster metering circuit at hr1. Returning now to the operation of the discriminating relays MA .. MD. If the call is a local one, neither of these is operated and speaking battery is fed to the called party over the windings of 1I. If however the call is to another exchange, MA and MC are operated if the wanted exchange is in zone 1, MB alone if in zone 2, MA, MB and MD if in zone 3, and MB, MC, MD if the call is to a manual board. Under any of these circumstances MA or MB are operated so that, as KR was operated at that time, BA in the first code selector operated and locked up so that when HR switches through the windings of 1I are connected in series across the outgoing junction. Metering and release of A-digit switch. The relapse of C described in the preceding paragraph prepares the circuit of DA (lower) which is completed by a pulse over cam S. DA locks up over its centre winding, completes an alternative circuit for A (upper), prepares the booster battery circuit at da5, and prepares a series circuit for its upper winding and DB (lower) which is completed, after an interval, by a pulse over cam Z. Relay DB locks over its upper winding, DA being released on cessation of the Z pulse. During the Z pulse, MC is operated once, twice or thrice according as to whether its lower winding is connected to leads 1, 2 or 3, and connects booster battery to the holding conductor 12 in the first code selector. On the relapse of DA, A falls back and short-circuits 1B which releases other operated relays in the A-digit switch and operates release magnet 1ZM. Relay K in the first code selector also releases and completes the homing circuit of ADF, relay B remaining held over k2, l2. In the case of a call to an operator, the battery feed is replaced by the loop 1I as previously described but metering is prevented. As MC is operated in this case, A and 1B fall back when HC relapses on completion of the sending of the digits. The A-digit switch releases as before and during the release period of MC and J an impulse from hc7 is connected to HR which switches through and, since K has now fallen back, locks up to ba3. Busy release. When the calling party replaces his receiver L, Fig. 1, and A, 1B, Fig. 2, fall back, and if this occurs during a flash battery period, battery on the positive junction wire operates 2I, Fig. 4, which holds J, C and therefore K, B, BA in the first code selector. At the end of the flash period 2I releases followed by J and C slowly in turn, the A-digit switch and ADF restore ; B and BA fall back to release the junction. Operator hold, recall of calling party. If the calling party replaces his receiver before the operator clears, battery at the manual board connected to the positive conductor operates MG which holds B, BA. The operator may ring the party by connecting ringing current to the negative conductor which operates OR since this relay is shunted by rectifier MRC. Local ringing current is thus connected up in place of relay L. Premature dialling. Switch ADF has not found an A-digit switch and K is unoperated. Incoming impulses step the first code selector so that the hunting circuit of ADF is opened at N2 and NU tone is connected up over N1. Lamp LP lights in circuit with an alarm (not shown) which operates after a delay. Forced release. When relay C operates on seizure of the A-digit switch, it prepares a circuit for TP (left-hand) which is operated by a pulse from the cam 1S, locks up to hc7 over its central winding and prepares circuits for G. If the calling party does not dial within a predetermined time, a pulse over cam 1Z operates G which locks up to ground at Ib3 and connects this ground over TP (right-hand) to the vertical magnet of the first code selector with results as described in the preceding paragraph. Relay A relapses and vertical magnet 1VM of the A- digit switch receives an impulse to send it off normal whereupon 1B is short-circuited, C, CA and K fall back, and ADF goes home. If the calling party replaces his receiver at the moment of seizur