Patent GB-717687-A (GB)
Title: Improvements in or relating to telephone or like systems
Inventor: BAKER GEORGE THOMAS
IPC: G11B20/16
Filed: 1951-07-25
Abstract: 717,687. Automatic exchange systems. BRITISH TELECOMMUNICATIONS RESEARCH, Ltd. July 10, 1952 [July 25, 1951], No. 17675/51. Class 40 (4) A telephone or like system employs a highspeed register device of the magnetic drum type such as is described in Specification 681,360, for recording the numbers of wanted subscribers on a time division basis. Contacts or an auxiliary track on the drum generate clock pulses, Fig. 2, five X areas corresponding to one Y digit block and 7 Y blocks to one Z space corresponding to a subscriber's number, several Z spaces being provided in the circumference of the drum. The reading and writing head circuits are shown in Figs. 4 and 5 and the wanted number control circuits in Figs. 7 and 8. An input on the A and B leads, shown in line 1 of Fig. 6, to the writing head circuit is amplified by V5 and passed to a toggle:circuit V6, V7 controlled by a sampling waveform (line 2), from the drum over lead SW1. The toggle produces two pulse outputs, one the inverse of the other, applied to V8, V9 (lines 3, 4), which direct alternate pulses from a continuous pulse supply (line 5), to one or other grid of a toggle V10 V11 (lines 6, 7) to produce an output (line 8) amplified by V12, V13 and fed to the writing head WH (line 9), positive pulses magnetising the unit area in one sense, i.e. a dot, negative pulses in the other sense, i.e. a blank. Line 10 shows the voltage generated in the reading head when this part of the magnetic track is read, the reading voltage being amplified by V14, V15, V16 and applied to toggle V17, V18 which also receives a sampling waveform on lead SW2 (line 11). The output is amplified by V19, V20 to produce two waveforms (lines 12, 13) on leads SL, SL, one the inverse of the other. The output on lead SL is a squared form of the input on combined leads A, B but displaced in time. Registration of called number.-The keyset shown in Fig. 7, which is also described in divided Specification 717,740, enters digits into space Z1 of the circumference of the drum. Operation of a digit key marks a common lead 15 and one or more leads 11-14 according to the binary code to control writing-in of the digit on a time-division basis. Memory toggle circuit M1 is operated in the first area of each scan by pulses on leads TX1, TY1 and pulses lead A to prevent any registration. Ml remains operated until the operator depresses and locks hold key H, when pulses on TX2, TY1 are extended over leads PE and B to effect a marking in unit area X2 of the instruction block Y1. On the next'scan the coincidence circuit on the right resets M1 so that steady erasure in the remainder of space Z1 no longer takes place. To register a digit 3, the operator depresses key 3 so that a signal is obtained on lead PE at time positions TX2, TX3. Also the key closes common circuit to leads TX3, TY1 to write a dot in the 3rd area of the first (instruction) block to operate memory circuit M2, the output of which is applied to a coincidence circuit whereby when the next storage block having no registration in the first position is found the memory circuit M3 is operated. M3 resets M2 and connects the train of signals from the digit 'key to the input lead B to write dots in the 2nd and 3rd areas of the first digit block, i.e. block Y2. At the end of the scan over the block concerned M3 is reset to prevent the digit being registered in any other block if the key is still depressed. At release of the key, potential is applied to lead PE so that when the dot in the 3rd area of the instruction block is detected M4 operates. A coincidence circuit then detects the first block in the group in which the first area is vacant, i.e. that in which the digit has just been registered and writes a "busy" dot in that space. Subsequent digits are registered in like manner in subsequent blocks. The digits registered can be sent out in the manner described in Specification 717,688. Restoration of the hold key erases the registration.