Patent GB-524141-A (GB)
Title: Selection controlling apparatus for telephone systems
IPC: H04Q3/42
Filed: 1938-11-25
Abstract: 524,141. Semi-automatic exchange systems. STANDARD TELEPHONES & CABLES, Ltd. Nov. 25, 1938, No. 34354. Convention date, Nov. 26, 1937. [Class 40 (iv)] In a key-controlled registersender, the digit registers are groups of hot or cold-cathode discharge tubes TAW ... TAZ, TBW ... TBZ &c. the conditions of which are transferred in succession to relays CW ... CZ with the aid of a further set of tubes DTW ... DTZ. These relays control the transmission of impulses by a sending chain which also measures two different lengths of interdigital pause at different stages. Registering number. On the seizure of the sender, SA pulls up and is followed by release reLay SB, the first pair of insequence relays FA. SE and relay SD which connects high positive potential to the lower electrodes of all the digit registers. The keys connect strong or weak positive or negative potential to wires T, R. In every case, one (or both) of two sensitive relays KT, KR pulls up and energizes the upper of the next pair of in-sequence relays GB, FB, GC, FC &c. Polarized relays KX, KY and marginal relays KW, KZ connect negative battery to the upper electrodes of the registers in the appropriate combinations. Certain tubes thus strike and continue to pass current over local resistances after the striking voltage is taken off by the release of the key. The relapse of KT, KR removes a shunt from the other one of the pair of in-sequence relays, and this connects up the next register and releases the preceding pair of sequence relays. The operation of the last sequence relay FE after the final digit has been registered connects the wires T, R' to the marginal relays ZA, ZB and disconnects the code receiving relays. This, as described in U.S.A. Specification 1,916,760, operates relays at the operator's position to energize ZA which locks in series with ZC. The operation of ZC disconnects ZA, ZB and connects half-battery to both pulse wires to disconnect the key-set. Sending number. Relay SC, which is energized on the seizure of the sender, completes a circuit for energizing polarized relays IA, IB in series and connects a resistance-condenser combination across the out-impulsing wires which are at present bridged by back contacts of the pick-up relay MA and front contacts of the impulsing relay IA. When in-sequence relay SE falls back after the registration of the first digit, a circuit is made for the first out-sequence relay OA which locks in series with TB which, for the moment, is short-circuited, connects the upper electrodes of the tubes of the first register to the upper electrodes of the decoder tubes DTW ... DTZ, connects high positive battery to the anodes of the tubes over the de-coder relays CW ... CZ. The decoder group thus takes up a condition corresponding to that of the first register. Relay OA also reverses the current through the left-hand windings of IA, IB, but their release is delayed by the discharge of condenser CN through their right-hand windings. On the relapse of IB the reverse current circuit is interrupted and the relays pull up'again after a delay imposed by the re-charging of condenser CN. The relays thus continue to pull up and fall back at a regular rate while any sequence relay OA, OB &c. is energized. The first relapse of IB energizes relay MB in the first counting pair and on its re-operation the other relay MC pulls up and energizes the pick-up relay MA. The next impulse energizes a counting pair depending on the digit to be sent. If it is 1, A, AA, if 2 or 7, B, BB, if 3 or 8, C, CG, if 4 or 9, D, DD, if 5 or 10, E, EE, and if 6, G, GG are operated. If the digit is 5 or less the chain builds up to the left from the energized pair to A, AA. If it is more than 6 the chain builds up to the left as far as B, BB, the next impulse energizes G, GG and the chain then builds up to A, AA omitting B, BB. If it is 6 the chain builds up to the left but' omits B, BB. On the operation of AA at the end of the last impulse of the first digit, MC, MB, and the pick-up relay MA are released. The next impulse from the interrupter pair energizes MD, ME which remove a shunt to allow transfer relay TB to pull up. The next impulse energizes F, FF in the counting chain and the chain builds up from this point to the pair C, CC to time the interdigital'pause, whereupon OA, ME, MD fall back, the de-coder tubes and relays are restored to normal and finally the counting chain relays are released. The remaining digits are sent in a similar way, the pause after the penultimate being of shorter duration than that after the previous digits owing to the operation of transfer relay TD. On the operation of A, AA to stop the final digit, HA is operated to remove a shunt from SA and so give a signal to the operator's circuit from which SA is then released whereupon SB falls and completes the release of the sender.