| 摘要 |
1,100,620. Transistor switching circuits. CREED & CO. Ltd. 20 Aug., 1965 [22 Aug., 1964], No. 35917/65. Heading H3T. In an electric pulse relay circuit when the amplitude of the input a exceeds a predetermined level stage 1 is caused to oscillate and when the amplitude of these output oscillations b reach a given value a monostable stage 2, which produces a pulse at c of longer duration than the period of the oscillator, is triggered to control a keying stage 3 arranged to supply D.C. to a load, such as a transistor T3 controlling the connection between telegraph wires 12, 13 for producing a pulse output at d. For an input telegraph signal a (Fig. 3, not shown), as long as the oscillations at b remain above the triggering value for the monostable circuit, pulses at c will continue to be produced until the end of the input signal. The input voltage at which T1 starts oscillating may be varied by resistor R2. A voltage dependent resistor R1 protects the oscillator 1 from overloading and diodes D1, D3 provide bias for transistors T2, T3. In a modified circuit (Fig. 2, not shown) an input signal a causes T1 to oscillate and trigger the monostable stage 2 which then starts to produce an output pulse c. The windings of a common coupling transformer are arranged so that the oscillations of the oscillator 1 are stopped until the end of the output pulse c at (t 4 , Fig. 3, not shown), when oscillations may start again to repeat the above operation. By suitable arrangement of the transformer windings the monostable circuit may either be triggered on the leading or trailing edge of the oscillator pulses. Two relay circuits may be arranged having their input connected in parallel (Fig. 4, not shown), so that input signals of opposite polarity operate one or the other circuit to switch a different pair of telegraph lines for double current working.
|
