Patent GB-717690-A (GB)
Title: Improvements in or relating to automatic telephone and like systems
Inventor: BAKER GEORGE THOMAS
IPC: B05B11/06
Filed: 1951-07-25
Abstract: 717,690. Automatic exchange systems. BRITISH TELECOMMUNICATIONS RESEARCH, Ltd. July 10, 1952 [July 25, 1951], No. 17679/51. Class 40 (4) A high speed register of the magnetic drum type compares the code digits of a dialled number with all possible code combinations. When coincidence occurs the appropriate translation is entered in place of the dialled code digits. The invention makes use of a magnetic drum such as is described in Specifications 717,687, 717,688 and 717,689 with extra translation and transfer tracks. Several memory circuits are provided, being set by coincidence of potential in the circuits on the left and restored by coincidence of potential in the circuits on the right. A pulse on lead A erases the record in the appropriate part of the drum while a pulse on lead B writes a dot. A called number is entered in a Z area comprising 14 Y blocks each of 6 X areas. The first Y block is used for control, Y2-4 for code digits, Y9-12 for numerical digits, Y13 for forced release and Y14 for control. The first and second X areas of .each digit block control writing in or reading off while areas X3-6 register the digit in binary form. Potential is provided on lead SL or SL according to whether the X area being read carries a dot or a blank. All tracks have their own reading and writing heads and the A, B, SL leads have suffixes D for the main register track, T for transfer, L for library and A for address. Assume that impulses have been registered as described in Specification 717,689 with the exception that the busy dot is entered in area X2 of each block instead of X1. When the C digit has been registered the busy dot in area X2 of block Y4 operates M1 which writes a dot in area X5 of block Y14 to indicate that a translation is required. M1 is then reset. When this registration is read at the next scan M2 operates to initiate the transfer of the A and B digits to the transfer track by pulsing lead BT while blocks Y2, Y3 pass under the reading head. M2 also enters a dot in area X2 of block Y14 to show that translation is taking place. M2. also operates auxiliary memory circuits MA-MD to reconvert the C digit into decimal form and select the required library track over lead SLL. During the scanning of the first block in the transfer track the busy dot in area X2 operates M3. Whenever there is a difference between the registration in the transfer track and that being read on the address track, M3 is reset by one of its coincidence circuits. However, when the appropriate part of the address track is reached there is agreement and M3 remains operated to operate M4 at the beginning of the next scan, M3 restoring at the end of the block.. M4 pulses lead AT to clear the transfer track and enter the registration from the corresponding part of the library track by pulsing BT. These digits are regenerated at 7-digit intervals round the transfer track until they can be used by the register concerned. This register is marked by a "translation proceeding" dot in position X2, Y14, and when this is detected by an auxiliary reading head SL<SP>1</SP>, M5 operates and the routing digits appearing on lead SL T  are transferred with the aid of VT3 from the transfer track to blocks Y2-7 of the main track D, wiping out the original code digits. M5 also resets MA-MD to dismiss the library track and with the aid of VT4 inserts dots in area X1 of blocks Y9-12 so that the numerical digits may be transmitted after the routing digits. In area X6, of block Y12, M5 operates M6 which resets M5, erases the "translating now" dot at position X2, Y14 and writes a dot in area X6 to initiate sending, which takes place as described in Specification 717,688. In code only calls, a special marking on the library track at position X1, Y8 is transferred to the transfer track and operates M6 earlier so that M5 is reset before the scan reaches the numerical digit blocks. In false code calls the special marking operates M7 to set up forced release. If there is undue delay in dialling at any stage the receipt of two TS pulses spaced by 30 seconds operates M7 to set up forced release.