Patent GB-664261-A (GB)
Title: Improvements in or relating to automatic switches for use in telephone or like systems
Inventor: PEARCE OWEN AVIS
IPC: H04Q3/00
Filed: 1949-02-02
Abstract: 664,261. Automatic exchange systems. AUTOMATIC TELEPHONE & ELECTRIC CO., Ltd. Jan. 5, 1950 [Feb. 2, 1949], No. 2822/49. Class 40 (iv). A two-directional switch is adapted to respond to three digits, the first digit determining the primary stepping and the second and third digits controlling the secondary stepping. As shown, a zone-metering selector having wipers W1 ... W4 is used to select one of a number of metering leads 1-6 under the control of two or three digits. The zone-metering selector is seized by a discriminating selector repeater DSR at a satellite exchange which places earth on the P lead when a subscriber dials " O " and operates relay B. The calling subscriber continues dialling, and the first code digit of the destination exchange is repeated by DSR over the + lead to relay A which controls the vertical magnet V. A slow-releasing relay C holds during the impulse train. The subsequent operation of the selector depends upon the value of the first digit, there being three possible cases. (i) First digit is " O ". Normal post springs NPA operate to energize relay H which disconnects the impulse repeating relay A and prevents further operation of the selector, the call being dealt with by an operator at the main exchange. (ii). First digit is between 1 and 8 inclusive. When relay C releases at the end of the first digit, relay E is operated to break the impulsing circuit to the vertical magnet V. The first impulse of the second digit energizes relays A, C, and CR and the rotary magnet R. At the end of the impulse, relay A releases but relay CR holds over the upper winding of relay WS which operates to connect up wiper W2 and de-energize the rotary magnet R which steps the wipers W1 ... W4 to their first contacts. The second impulse operates relay A to release relay CR, WS holding over its lower winding, and the end of the impulse release relays A and WS, switching from wiper W2 to W3. The third impulse proceeds similarly to the first, stepping the wipers to their second contacts and switching back from wiper W3 to W2. Impulsing continues in this manner, the selector stepping on the odd-numbered impulses, with wiper W2 connected on the odd impulses and W3 on the even impulses. If the second digit is not 9, relay C releases at the end of the impulse train and is followed slowly by relay E. In the interval relay H operates to send an impulse over the - lead to the discriminating selector repeater DSR which is thereby prevented from sending further impulses to the selector. Relay H also switches the + lead from relay A to relay ST in preparation for the metering start pulse. If, however, the second digit is 9, so that the impulse train ends with relay CR operated and the wipers W1 ... W4 on their fifth contacts, a relay DO is operated by battery applied to the fifth contacts of levels 1-8 of the wiper W4. This prevents the operation of relay H and disconnects wipers W2 and W3. Relay C releases as before, causing this time the energization of relay RR. A third digit is now received and operates similarly to the second, but the wipers W1 ... W4 now step over their contacts numbered 6 to 0. Relay C again operates, releasing relays DO and RR, and, at the end of the impulse train, relay H operates as before to prepare the circuit for the metering start pulse. (iii). First digit is 9. Normal post springs NPB operate, bringing up a relay DA to complete a self-interrupting circuit for the rotary magnet R to restore the switch to normal. Thus the first digit is absorbed. Relay DA holds in series with relay DR which operates, connecting up wiper W1 and setting the circuit to respond like a final selector to the second and third digits. Metering. The metering start pulse from the discriminating selector repeater DSR operates the metering start relay ST to connect the S pulse lead 11 to relay MA which operates on the first S pulse. The first Z pulse over lead 12 energizes relay MB and the selected metering lead 1-6 is now extended over the - lead to the discriminating selector repeater where a metering relay is operated to control the calling subscriber's meter. Relay MA releases when the Z pulse ceases at the end of the first metering cycle. The second S pulse brings up relay MC and the second Z pulse energizes relay MD whereupon relays ST and MB fall back, and the selected metering lead is again connected to the - lead. If only two metering cycles are required, e.g. for a night rate, the cessation of the second Z pulse releases relays MC, MD and the circuit is restored to normal. If, however, three metering cycles are required, e.g. for a day rate, battery is applied to lead 13 and operates relay TC during the second Z pulse in order to connect relay MA to lead 11  when MC restores at the end of the second metering cycle. The third cycle is similar to the first, but MB restores as well as MA at the end. The whole sequence of operations may be repeated at predetermined intervals.