Patent GB-642538-A (GB)
Title: Improvements in or relating to alternating current signalling equipment systems
Inventor: WRIGHT ESMOND PHILIP GOODWIN
IPC: H04Q1/45
Filed: 1946-01-18
Abstract: 642,538. Automatic exchange systems. STANDARD TELEPHONES & CABLES, Ltd. Jan. 18, 1946, No. 1631/47. Divided out of 642,524. [Class 40 (iv)] In a voice frequency signalling system digits and supervisory signals are transmitted in a code employing two frequencies only, each signal consisting of one or two pulses, some comprising one, some the other, and some both of the two frequencies. Outgoing termination. The digits to be sent are stored in the relay-register (Fig. 1), two pairs of relays, each comprising an X and a Y relay e.g. AX, AY, being provided for each digit. Each of the pairs prepares for the sending of one pulse, the operation of the relays being controlled from a key-sender so that a relay is operated only if the frequency to which it corresponds is to be included in the pulse it controls. On the release of a depressed key the Z relay associated with the digit storage group pulls up in series with the operated storage relays and transfers the relay-controlling leads to the next group. After keying all the digits required the operator depresses the key ES which brings up the end of selection relay ZXY. The receipt of the proceed to send signal at the outgoing termination (Fig. 2) brings up EX followed by B thus starting the sending switch AR, which advances step-by-step to the fifth position, relays FX and/or FY pulling up in the second and fourth positions, over contacts of the first and second pairs of storage relays of the first digit group, to send the code signals corresponding to the first digit to line. Provision is also made for stepping the switch from the fourth position if the coded digit comprises one pulse only. The switch steps off the fifth position and continues sending the digits stored, under control of the storage group relays. After sending the last digit AR will be in the first position of a group of 5 and cannot advance as the controlling Z relay is back. However, in such a position, ZXY brings up C over wiper arm1, followed by FX and FY, and AR advances to the fifth position, FX and FY remaining up in position 2, and FY alone coming up again in position 4 to transmit the end of selection signal, XY, Y. In the fifth position operation of E releases all the relays of the storage groups, and the switch homes, F coming up momentarily in the home position to release D, E, and B. Incoming termination (Fig. 3). It is assumed that the reception of a seizing signal results in the association of a register, terminating in the operation of TT in the register and CF, and CFF in the line circuit in well-known. manner, a proceed to send signal being sent as described in Specification 642,524. Relays GX and/or GY in the receiver respond to the first incoming pulse, followed by XA and/or YA, K pulling up in series with the operated storage relay and bringing up KK. At the end of the pulse the operated G relay or relays and relay K release and ZA comes up to switch in the second pulse storage group. If there is no second pulse, ZB comes up at the end of the release period of KK and switches in the first pair of relays of the second digit storage group (not shown). However, if there is a second pulse, the release of KK is ineffective, since XB and/or YB come up under control of GX and/or GY, and ZB does not operate until K releases at the end of the second pulse. Reception of digits on each set of storage relays is identical. The stored digits are converted into numerical form by an output sequence switch SC and a counting switch RS. Switches SC and RS are stepped in well-known manner, the latter being stopped. by the operation of SS over contacts of the storage relays and contact banks rsm1, and 2, this operation also serving to advance SC to send the next digit. Operation of ZZ to the end of selection signal stops the selection operations and initiates the next step in the setting up of a connection.