| 摘要 |
980,956. Transistor pulse amplifier circuits; keying circuits. STANDARD TELEPHONES & CABLES Ltd. Feb. 23, 1962 [Feb. 28, 1961], No. 7066/62. Headings H3R, H3T and H4P. A bi-stable circuit suitable for use as a telegraph repeater comprises an amplifier fed from a source of oscillators through a gate and feeding a rectifier which provides both the output signal and a feedback signal which maintains the gate open when open and closed when closed. In Fig. 1 a sine or square wave signal is applied via C1 and a D.C. restorer C2, G1 to a transistor amplifier T2 the output of which is rectified and smoothed at G2, C3, R4 before application to a load R5, the voltage across the load being clamped at + 60 V. by a rectifier G3. The D.C. output is also fed through R6 to maintain a transistor T1 non-conducting. If a positive triggering pulse is applied via C5, transistor T1 is rendered conducting short-circuiting the input to the amplifier so that the rectified output voltage falls to zero. The voltage now fed back through R6 maintains T1 conducting so that the output remains zero. The circuit may be restored to the original state by applying a positive pulse to C5. Fig. 2 shows two such arrangements using transistors of opposite conductivity and operative alternatively so that rectifiers C3 clamp the voltage across the load R5 at + 60 V. or - 60 V. depending on which circuit is operative. Rectifiers G4 and G4 1 in the input circuit limit the amplitude of the A.C. signal applied through R9 and R<SP>1</SP>9. |
