Patent GB-908230-A (GB)
Title: Improvements relating to automatic telecommunications switching systems
Inventor: CARTWRIGHT JOHN CONRAD
IPC: H04Q3/42
Filed: 1960-01-28
Abstract: 908,230. Automatic exchange systems. ASSOCIATED ELECTRICAL INDUSTRIES Ltd. Jan. 16, 1961 [Jan. 28, 1960], No. 3139/60. Class 40 (4). In an exchange system having a common control circuit for a plurality of selectors in a switching stage and a plurality of registers which may be taken into use simultaneously for a number of different calls, each selector has first and second individual relay means, the second means being operable in response to the first means so as to associate the control circuit with the selector (or selectors if more than one first relay means has operated) and to prevent the operation of the second relay means in all the selectors in which the first relay means has not operated at this time. A register which serves for setting all the selectors required for extending a call through the exchange is shown in Fig. 1. The code selecting elements DE1-DE10 may be banks of uniselectors which are set by incoming dialling pulses, each bank contact being connected to a source of high or low resistance plus or minus battery so that markings may be applied to subsequent selector switches. The network N1 serves to apply these battery conditions to elements DE1- DE5 and thence to - wire LLd, and network N2 feeds elements DE6-DE10 and thence to + wire LLd. When sufficient routing digits are registered, first relay means (HA, HB) in the first group selector (Fig. 2) are operated and these associate, by means of second relay means (CA), the common control circuit (Fig. 3), when free, with the selector (or selectors, if other relays HA, HB, in other selectors have operated). The sequence switch SS (Fig. 1) then initiates the transference of the marking codes contained in the register to marking relays u-z (Fig. 3) and thence to marking banks M of the first group selector GS. When the first group selector is set in accordance with this marking, the process is then repeated for each set of selectors required for completing the connection of the call. Setting up call. First group selector.-A register, Fig. 1, is taken into use for a call and incoming dialled digits are stored in a uniselector digit store DS with consequent setting of the code selecting elements DE1-DE10. During, or at the end of, registration of these digits, a start relay (not shown) operates and at its contact st1 earths the outgoing P-wire which causes relay HA followed by HB in the first group selector, to operate and at its contact st2 initiates the first step of sequence switch SS. HA and HB hold to the P-wire until the common control circuit (Fig. 3) is free (CB released) and when this occurs relay CA operates over its right-hand winding and holds over its left-hand winding in series with relay CB and off-normal contacts N. Contacts ca2, and duplicate contacts ca2<SP>1</SP> in parallel therewith, are thus connected in a series chain SC including corresponding contacts of the operated CA relays of the other selectors served by the common control circuit, so that a relay CC in a selector having operated ca2, ca2<SP>1</SP> contacts " closest " to the control circuit will be the first CC relay to operate. Eventually therefore the relay CC shown in Fig. 2 must operate and thus the code elements DE1 and DE6 in the register are switched through to the marking relays U-Z and RHA in the control circuit. Then either U or V and at least one of relays W-Z and RHA will operate, the latter relays being held to battery on holding wire l, while the former bring up UA or VA respectively. Relay PA (Fig. 1) pulls up in series with the operated U or V relay and in doing so releases relay PL (Fig. 1) which was operated when the register was taken into use, PL in turn releasing PA. Magnet SSM however was briefly energized by the operation of PA and on the latter's release, causes the sequence switch to step on to its third contact. Relay SWA pulls up in series with X, W (Fig. 3), the latter however not operating, and brings up SWB followed by SWC. In the control circuit, the operation or otherwise of RHA causes the release of HA or HB which also act as wiper switching relays for the group selector so that one of the (two,) hundred outlet rows per bank of the switch is selected. The release of PL drops out U or V and start relay SK pulls up to initiate hunting by the group selector for the marked outlet or group of outlets in the marking bank M. As soon as a free outlet is found, test relay T operates and stops the hunting action by connecting relay TA in series with the selector driving motor GSM. On operating, TA releases CC and hence CA so that the line is connected through to the next selector. Release of CC also drops out SWA followed by SWB and SWC but before SWB finally falls magnet SSM is energized and relay LC is connected to - wire LLd. If there is congestion, the + and - wires LLd are short-circuited over the + and - wipers of selector GS and LC operates so as to hold SWB. However, if SWB is allowed to release, the sequence switch SS steps on and extends the code selecting elements DE2 and DE7 to the marking relays in the control circuit of the second group selector. Relay CB (Fig. 3) remains up until all the selectors in which relay CA has operated have been attended to, the control circuit then being seized by the next batch of selectors having operated HA and HB relays. Final selector.-It is assumed that the register sets the final selector in accordance with the last two digits stored and a modified system of marking relays in the final selector common control circuit is described with reference to Fig. 4 (not shown).