Patent GB-360627-A (GB)
Title: Improvements relating to automatic telephone systems
IPC: E02F3/90
Filed: 1930-10-20
Abstract: 360,627. Automatic exchange systems. SIEMENS BROS. & CO., Ltd., Caxton House, Tothill Street, and DIXON, R. G., 162, Westmount Road, Eltham Park, both in London. Oct. 20, 1930, No. 31399. [Class 40 (iv).] In a system suitable for a small number of lines, the line circuits comprise relays for connecting a line to one or other end of an idle link circuit according to whether the line is calling or called, and the link circuits each comprise a marker which responds to dialled impulses and, over a single path, seizes the wanted line and operates the requisite relay for connecting it to the link circuit. A line circuit comprises a line relay for each link circuit, and a cut-off relay; in the case of a calling line a line relay is operated alone, while for a called line the cut-off relay is operated in addition to a line relay. In the system shown in Fig. 1, a line circuit shown in the left-hand dotted rectangle has access to the link circuits one of which is shown in the upper right-hand rectangle, an all otter and common ringing and tone equipment being shown in the lower right-hand rectangle. The line circuits are multipled to the calling and called sides of the link circuit which comprises a common feed over relay A. The marker consists of a chain of single relays. The system shown in Fig. 2 is similar but has modified line relay arrangements, and a marker comprising relays operated in different combinations. More than two link circuits may be provided, connection of a line to a particular link circuit being effected by line relays singly or in combination. First arrangement, Fig. 1. When a call is made, start relay ST operates over the calling loop in series with LB(i) which remains inert. Relays P and Q are energized but P pulls up first, disconnects Q, operates relief relays PA, PB so that LA(i) is switched into the calling loop in place of LB, and ST(i) is short-circuited to permit LA(i) to pull up. If the link circuit shown is busy, P is short-circuited by ground at b2 and Q operates to short-circuit ST(i) and permit LB(i) to operate so that the calling loop is connected to the other link (not shown) associated with the lower branch of the line circuit. If both circuits are busv SA pulls up over the b5 contacts in series and disconnects ST. Assuming the link shown to be idle, A operates over the calling loop, LA locks up over (ii), CO(ii) is disconnected, and B pulls up to connect holding ground and release P. If no other line is calling ST also releases. Relays M, C, TR(i) pull up and tone generated by relays R, RR, and to be used subsequently for ringing, is connected over m3, h7 to give the dialling signal. Relay Z which differentiates between digits not exceeding and exceeding 5, pulls up. The dialled impulses repeated by A operate and release U .. Y in turn, M being released on the first impulse so that Z is dependent on Y and U, and falls back during the time both these relays are operated (sixth impulse). When C falls back at the end of the train, ground from b2 over relay H and one of the bracketed marking leads determined by the operation of the counting chain, operates winding (i) of cut-off relay CO (not shown) of the wanted line. Winding (ii) would have been operated if the other link circuit had been used since the markers are individual to the links. Relay CO operates the LA relay of the wanted line and both lock to b2 and these relays in conjunction switch the contacts tr3, tr4 to the wanted line. LA disconnects the marking wire from the other link to CO(ii). Relay H re-operates C over a contact of the operated counting relay to release TR(i) which completes the connection of relay R to the wanted line and this relay interacts with RR to produce intermittent reversals of current flow over the wanted line to ring the bell thereat. The counting relay falls back. When the called party replies TR(ii) operates and connects his line to relay A which thus feeds both calling and called lines. If the wanted line is busy H and C remain unoperated and TR(i) falls back to connect busy tone from vibrating relay BT over tr8, h7 to the calling party. Tone from relay BT is of higher frequency than the ringing current produced by R, RR. Modified arrangements, Fig. 2. Relay ST pulls up over the calling loop in series with LA(i), LB(i) which only operate their armatures la1, lb1. ST completes circuits for P and Q and, as before, P or Q operates, but in this case a full operating circuit for LA(ii) or LB(ii) is completed. Assuming LA is operated, A and B pull up, relays R, RR start interacting, and tone passes over c4, h5 to the calling party. TR(i) pulls up, prepares circuits for the marking relays V .. Z, and when C has operated, de-energizes the tone equipment. The dialled impulses operate relays V .. Z in various combinations and when C falls back, H pulls up in series with CO(i) and LA(ii) of the wanted line, all contacts of LA being operated. TR falls back, and C(ii) reoperates since at least one of relays W, Y, Z is operated, locks up, releases the marking relays and removes a short-circuit from TR(ii). The tone equipment is started up and the remaining operations take place substantially in the manner described for the first arrangement.