| 摘要 |
531,554. Wireless signalling. STANDARD TELEPHONES & CABLES, Ltd., and SPAGNOLETTI, P. H. July 5, 1939, No. 19566. [Class 40 (v)] A radio telegraphic system is provided with automatic means under the control of the keying device for interrupting the operation of the master oscillator at the transmitter when the keying device remains unoperated for a predetermined time. The key C operates a relay A having a pair of contacts a<SP>1</SP> which when closed connect H.T.+ via conductor K to the keyed stage of the transmitter not shown. A second pair of contacts a<SP>2</SP> when closed cause energization of relay B to close contacts b<SP>1</SP> thus connecting suitable bias from H.T. over conductor O to the master oscillator not shown. Relay B also controls change-over contacts b<SP>2</SP> for connecting the aerial lead AN to the transmitter lead T or receiver lead R. Relay B is made slow to release such as by a slug S. Thus during normal transmission contacts b<SP>1</SP>, b<SP>2</SP> remain in a position to energize the oscillator and to connect the aerial for transmission. If however key C remains open for a given time, relay B drops off to render the oscillator inoperative and connect the aerial for reception. |
