| 摘要 |
939,809. Magnetic recording circuits. SIEMENS & HALSKE A.G. Aug. 15, 1960 [Aug. 14, 1959], No. 28177/60. Class 40 (2). [Also in Groups XIX, XL (b) and XL (c)] A circuit for producing a response to input pulses which may be of variable amplitude, for example pulses read from a magnetic tape, at the instant at which their amplitude is at its maximum, comprises means for differentiating the input pulses and means for producing a response at the instant at which the polarity of the differentiated signal changes, said latter means being conditioned to respond only during the intervals at which input signals are applied to the circuit by a gating circuit controlled by the application of the input pulses thereto. Input pulses S1, S2 are applied at E to a transistor amplifier T1 through a differentiating circuit C1, R1 so that differentiated signals S1<1>, S2<11> are applied from transistor T1 to the input of a Multiar circuit comprising a transistor T2 with feed-back through a transformer Tr from its collector to its base, the diode D permitting the feed-back to be effective only when the differentiated signal goes negative so that the circuit is triggered to produce a response at the output A at the instant at which the differentiated signal changes polarity from positive to negative. To prevent the operation of the circuit by spurious signals, a monostable-state circuit comprising transistors T3, T4 operates as a threshold circuit controlled by the input signals, the level at which the circuit operates being determined by the choice of resistors R4, R5. An input pulse switches the monostable circuit which provides an output to render transistor T5 conducting, thus completing the circuit from the source UB through the emitter-collector circuit of transistor T2 to earth. |
