Patent GB-354459-A (GB)
Title: Improvements in or relating to telephone systems
IPC: H04M1/272
Filed: 1930-06-06
Abstract: 354,459. Automatic and semi-automatic exchange systems. COVENTRY AUTOMATIC TELEPHONES, Ltd., COLLYER, J. E. and CARPENTER, O. I., of General Electric Co., Stoke, Coventry. June 6, 1930, No. 17531. [Class 40 (iv).] Keyboard senders consisting entirely of relays comprise storage groups less in number than the maximum number of digits to be sent, a counting chain, and a distributing group for controlling the sequence of operations. Current supply may be derived from D.C or A.C. mains, the A.C. supply being rectified and, if desired, smoothed as described in Specification 336,802, [Class 40 (iv), Telephones &c.]. Current consumption is small, and the sender may be used at a P.B.X, subscribers' substation or elsewhere where an exchange battery is not available. As described, the digits, which may be seven in number, are keyed on a single strip and stored in five groups AX .. AZ &c., the first two groups being released in time to receive the last two digits. The distributing group A, AA, B, C controls in part the holding circuits of the storage groups and also the connection of the marking contacts to counting chain D, NA . . NE which runs through an extra cycle from NA for digits over 5. Impulses may be supplied by a pendulum interrupted INT as described in Specification 311,921, [Class 40 (iv), Telephones &c.]. Registration of digits. Start key DK operates HD which lights lamp EL and grounds the points indicated by a circle. The first five digits are stored in turn, the key-leads being extended to the storage groups in turn by relays KA . . KE over which the storage relays are held. As will be described later, A and B will have operated when the first two digits have been sent, so that the first two storage groups are released but KA, KB are held dependent on KE which operates after the fifth digit has been stored so that the keyboard may again be connected to the first two groups in turn. When the seventh digit .is keyed, B will still be operated, but ST prepares a circuit for KB when it operates due to energization of DS when the seventh digit is keyed. No further digits can be stored since although C operates when the third digit is transferred to the counting chain and releases the third group, relay KC remains held. The fourth and fifth groups hold until HD is released by restoration of the start key. Transmission of impulses. The first digit is transferred immediately to the counting chain D, NA . . NE and, if the digit is 1 to 5, X also operates to prevent the chain running through an extra cycle from NA. When the first digit key is released, DS falls back, and P operates over a contact of the operated chain relay, and at p7 removes the marking ground and locks the chain relay. The pendulum interrupter magnet has been energized so that P also operates SA which locks up, opens the shunt across the impulse contacts im3 in the loop LO, LI, and releases the magnet so that the pendulum armature sends pulses to IM, which pulses out over the loop and runs the chain down under the control of E F which operate alternately. If X has been operated (digits to 5), SZ operates (sa2, x3, im2, f2, ne5, sz1) when NE pulls up (nd2, f4, im1, sz1), SA falls back, shunts the loop and opens the circuit of SZ which releases slowly. When IM next operates, X and F fall back, NE and P release and G pulls up to hold HD and prepare a temporary alternative holding circuit for the counting chain. If X had not been operated (digit 5-0), there would be no circuit for SZ when NE pulls up. When however F falls back on the next operation of IM, a circuit is prepared for sending an impulse to NA on the next relapse of IM, and is operated X so that the chain runs down from NA and a further five impulses are sent. Distributing relay-group. When HD is operated by the start-key T pulls up and is held by P which operates on release of the first digit key. Relay AA pulls up in series with A to prepare the second digit marking-circuit which is made effective by the relapse of P after the first digit has been sent out. Relay T is also released by P so that when P reoperates subsequent to transfer of the second digit to the counting chain, B pulls up to prepare the third digit marking-circuit which is completed on the next relapse of P which also operates T. The next operation of P subsequent to transfer of the third digit to the counting chain operates C which prepares the fourth-digit marking-circuit. The third digit having been sent out, P relapses and on re-energization releases A, AA (T having been released on the relapse of P) so that the fifthdigit marking-circuit is prepared. This marking- circuit is completed on the relapse of P (fourth digit sent) which also operates T so that when P reoperates, B and C both fall back and the marking- circuit for the sixth digit (first storage group) is prepared. The operation for the sixth and seventh digits is similar to that for the first and second. Cancellation. Relay CK, operated by the cancel key K, energizes SA and locks, opens the loop to release the partly set up connection, releases P and HD so that all operated relays, including SA and CK, restore.