Patent GB-753689-A (GB)
Title: Distributor utilising transistors
IPC: H04L13/14
Filed: 1954-03-23
Abstract: 753,689. Transistor multi-stable state circuits. TELETYPE CORPORATION. March 23, 1954 [April 20, 1953], No. 8460/54. Class 40 (6). [Also in Group XIX] A number of transistors are arranged in a chain or ring in such a manner that each can have one or other of two states, one transistor being in the first state and the remainder in the second state. Pulses are fed to the first transistor to cause it to take up the second state, thereby generating a pulse to cause the succeeding transistor to pass to the first state. The circuit may be employed for counting (see Group XIX) or frequency division of pulses or in a distributer. The transistors 10 ... 13 are connected in a ring, Fig. 1, the collector of transistor 10 being coupled over capacitor 30 to the base of transistor 11 and so on. Each collector is connected to an output load 15 ... 18, the emitters being coupled over rectifiers 22 ... 25 to a line 27 fed with negative-going pulses derived from square-wave generator 45 having a rectifier 47 across the secondary of transformer 46 to pass only negative-going differentiated pulses. One of the transistors, for example 10, takes up a conducting state, the resulting current flow establishing a low emitter voltage so that rectifier 22 conducts, the remainder of the rectifiers being cut-off since the associated transistors are all non-conducting and thus have relatively high emitter potentials. Input pulse A1 Fig. 3, applied to line 27 is effective over rectifier 22 to lower the emitter potential of transistor 10 which passes to the cut-off condition, the collector potential falling accordingly. A negative-going pulse is fed to the base of transistor 11 due to the differentiating action of capacitor 30 so that the transistor is driven into the conducting state, the emitter falling in potential until rectifier 23 conducts to prevent any further fall. The collector rises to a potential near that of the base, the next input pulse A2 causing the potential to fall again to trigger transistor 12 into the conducting state. When transistor 13 is rendered conducting, the rise in collector potential causes a pulse to be fed over capacitor 33 to the base and hence the emitter of transistor 10 but this is ineffective and is blocked from the line 27 by rectifier 22. In a modification, Fig. 4, to allow the conducting state tb be progressed from right to left or vice versa a second series of coupling capacitors is included from the collector of each transistor to the base of the transistor immediately -to the left. Rectifiers 72, 74, 76 and 78 are arranged in the path feeding from left to right and rectifiers 77, 75, 73 and 71 in the reverse path. Either path can be biased off from a two stablestate circuit comprising transistors 56, 57. If transistor 57 is non-conducting then the collector is very negative and rectifiers 72, 74, 76 and 78 are biased to the conducting state so that the first path is effective, the reverse path being biased off by the more positive potential of the collector of transistor 56. Pulses from generator 81 progress the conducting state from left to right until the bias conditions are reversed due to a change-over in the circuit 56, 57 caused by a positive pulse from generator 85. The initial conditions may be restored by a positive pulse from generator 89. An output transformer may be included in the collector lead of the transistor, Fig. 5 (not shown).