| 摘要 |
1,038,517. Radio signalling. FLIGHT REFUELLING Ltd. Oct. 30, 1964 [Nov. 18, 1963], No. 45473/63. Heading H4L. In a battery-operated portable radio receiver responsive to a calling tone or tones, in order to conserve the battery, means are provided for automatically switching the receiver " on " and " off " for predetermined periods and for locking the receiver " on " upon the receipt of the appropriate calling signal, the output stage of the receiver drawing current only when the receiver is locked " on " and the remaining circuits drawing current only during the predetermined " on " periods and during the locked " on " state. As shown in Fig. 2, a paging receiver 2 to 10 is provided with a complementary pair transistor multivibrator 16, Fig. 3 (not shown) which in the " standby " position of switch 25 and the absence of the appropriate calling signal causes the battery supply for the receiver circuits 2 to 9 to be interrupted. In this position the switch 25 also disconnects the output stage 10 and converts it into an A.F. oscillator. The output of the amplifier 8, in addition to supplying the output stages of the receiver, supplies an amplifier and resonant reed unit 13 responsive to the calling signal, which via a transistor switch 15 locks the multivibrator 16 in its " on " position on receipt of the correct calling signal to maintain the supply current for the receiver. This causes the oscillator 10 to produce an audible note in the loud-speaker and when the switch 25 is moved to the " receive " position the receiver is operative for normal speech reception. In an alternative arrangement, cessation of the tone signals causes the multivibrator to revert to its normal switching cycle. |
