| 摘要 |
989,436. Electric selective signalling systems. INTERNATIONAL BUSINESS MACHINES CORPORATION. Feb. 8, 1962 [March 31, 1961], No. 4909/62. Heading G4H. [Also in Division H3] A circuit for driving a current pulse through an inductive line comprises a transistor having an emitter resistor and a base clamping device and having its collector connected to one end of the line and via a resistor to a reverse bias voltage so as to maintain the collector/base capacitance charged. As shown in Fig. 6, all transistors are normally non-conductive. When it is desired to pass a current pulse from right to left in line 1, a positive pulse is applied to the base of transistor T3 so that transistors T4, T5 are also made conductive. A negative pulse applied to the base of transistor T2 drives transistor T1 into conduction so that a constant current pulse travels in line 1 via diodes D1, D2. A current pulse may be driven from left to right by applying control pulses to transistors T<SP>1</SP>2 and T3<SP>1</SP>. Fig. 7 (not shown) relates to a storage matrix in which bipolar pulses may be driven through any one of thirty two lines under control of twelve voltage pulse generators and twelve current pulse generators. Reference is made to control of an n x m matrix by 2(#n + m) drivers. Simpler switching circuits are described (see Division H3). Digital-analogue conversion. Fig. 8 shows an arrangement in which current pulses can be driven in either direction along a selected one of lines 1, 11, 111. Transistors T1 are normally non-conductive; digital data pulses being applied to terminals Gi, the appropriate line being selected by voltage pulses applied to terminals Vg. The amplitude of current pulse in any line 1, 11, 111 is dependent on the values of emitter resistor Re or clamping voltage VX, so that these values are selected so that the constant current through any transistor T1 is weighted according to the value of digital data fed to its base. If more than one transistor T1 is made conductive, the current in the selected line is equal to the sum of transistor currents. |
