Patent GB-926056-A (GB)
Title: Improvements relating to automatic telephone exchange systems
Inventor: LONG DOUGLAS PERCY
IPC: H04Q3/42
Filed: 1960-10-11
Abstract: 926,056. Automatic exchange systems. ASSOCIATED ELECTRICAL INDUSTRIES Ltd. Sept. 28, 1961 [Oct. 11, 1960], No. 34805/60. Class 40 (4). In a control circuit, common to a number of selectors, an arrangement for marking selected outlets of an associated selector is set, in accordance with digits stored in a register, by code signals transmitted from the register of an associated translator, over a marking multiple common to a plurality of such control circuits, it being arranged that the common multiple is used on a one-call-at-a-time basis. A transmission bridge circuit and an associated individual group selector (Fig. 1) are taken into use for a call and one of a plurality of registers is coupled to the bridge circuit. As soon as the first digit is stored, a test circuit in the register periodically tests the condition of a control circuit common to a plurality of first selectors and seizes it when it becomes free. A similar periodic test is then made for a translator common to the whole exchange. A " translation " of the digit is then applied as a code signal over a common marking multiple MM to all the control circuits associated with first selectors (and also to those of subsequent selectors), a marking arrangement in the relevant control circuit thus being set so that the first selecto may be stepped to a marked outlet in the wanted direction. A similar procedure is adopted for all the subsequent selectors taken into use for the call. Fig. 3 shows a system which dispenses with a translator, marking multiples common to each stage of selectors then being required. This latter system is particularly described with reference to Figs. 6A, 6B, 6C (not shown). Setting up of a call (Figs. 4A, 4B, 4C, 5A, 5B arranged in that order).-Relay A comes up to the calling loop and impulse receiving relay AA in a free register follows. Release relay BB is energized so as to busy the line circuit (contact bb3). Dialling relay CD responds to the first dialled digit and the thousands digit switch DA is stepped by AA, sequence switch DR moving off-normal at the end of the digit. Relay M (Fig. 4B) then comes up to initiate the cyclic operation-relapse of relay G. Capacitor C2 (Fig. 4C) is thus connected periodically to highspeed test relay TC but this has no effect if the common control circuit is busy as C2 discharges through a low resistance winding II of the operated TC relay in another register. As soon as the control circuit is free, however, and C2 is connected to TC, then the latter operates and holds over its winding II. Relay TD comes up to allow a further test relay TM to test the translator. When the latter tests free TM locks-up and is followed by TN and TR. Digit switch DA is connected to the translator and the latter applies earth marking on one or more of the wires MW-MZ of the marking multiple extending to all the control circuits. With TN up, relays K and KT (Fig. 5A) come up in series to couple the marking relays AW-AZ to the marking multiple. Start relay SS operates in series with any operated AW-AZ relays so that when KT falls back (see below) the selector hunts for an outlet marked by the marking tree of contacts of AW-AZ. Test relay TA pulls up when a free outlet is found to stop the hunting and to operate TB. Switching relay H follows and the control circuit is released from the connection. Operation of TN also releases G and M (Fig. 4B) so that eventually TN and thus KT and TR fall back, whereby the translator is released from the connection, digit switch DS is stepped off-normal and TM is released. As mentioned previously if a free second selector is found TB operates, thus causing TC and TD (Fig. 4C) to fall back. When the second digit is received DR steps on and M comes up so that the above procedure may be repeated for the second and subsequent selectors. DR eventually reaches its fifth contact and M operates as before but in this case it is assumed that a final selector has been reached so that the tens and units digits are translated simultaneously and the marking multiples MW-MZ and FMWFMZ are both used. If the wanted line is idle TC and TD are released by the operation of a test relay in the final selector and since DS is now on its fourth contact switching relay B operates and the register is released. If all outlets of a selector are busy then a last contact relay LC (Fig. 5B) comes up followed by LD. TA pulls up with LC so that TB and H can operate to release the control circuit and busy tone is reverted over the last contacts of SW1, SW2. The operation of LD connects the control circuit to an overflow meter (not shown).