公开(公告)号：KR780000303B1

公开(公告)日：1978-08-10

申请号：KR700000026

申请日：1970-01-08

Applicant: MOTOROLA INC

Inventor： LUNDGREN K P

IPC: H04W88/18

公开(公告)号：HK12276A

公开(公告)日：1976-03-12

申请号：HK12276

申请日：1976-03-04

Applicant: MOTOROLA INC

Inventor： LUNDGREN K P

IPC: H04W88/18 ,  H04Q7/02

Abstract: 1,234,915. Radio signalling. MOTOROLA Inc. 31 Dec., 1969 [10 Jan., 1969], No. 63447/69. Heading H4L. A radio transmitting and receiving apparatus uses common encoder-decoder equipment including a continuously operating oscillator for responding to or transmitting a calling tone. The encoder-decoder comprises a filter 18 coupled to the output of the receiver discriminator 16 for selecting the tone signal, the output of the filter being supplied via an amplifier 72 to a reed filter 32 which is resonant at the tone frequency. The output of the reed filter is supplied via an amplifier 36, feedback amplifier 41 and amplitude limiter 19 to the input of the amplifier 72 to form a tone signal oscillator which is coupled via potentiometer 45 to the modulator 11 of the transmitter to transmit the calling tone when the apparatus is switched to transmit. On reception, the received tone signals are of much greater amplitude than those supplied from the limiter 19, producing a much greater output from the reed filter 32 and causing a normally cut-off detector 58 to conduct and discharge a capacitor 62, whereby a transissistor 59 is cut off. This removes muting from the receiver amplifier 17 so that the output of the discriminator is coupled to the audio output circuits. Removing the microphone from the hang-up box 61 or operating a switch 60 also renders the amplifier 17 operative.