公开(公告)号：US3614621A

公开(公告)日：1971-10-19

申请号：US3614621D

申请日：1969-08-08

Applicant: MOTOROLA INC

Inventor： CHAPMAN RONALD H ,  MOORE GEORGE G

IPC: H04B1/40 ,  H03J5/24 ,  H03J7/18 ,  H03J7/20 ,  H04B1/16 ,  H04B1/36

CPC classification number: H03J5/246 ,  H03J7/18

Abstract: A channel scanning and priority channel monitoring circuit for a multifrequency receiver utilizes a bistable multivibrator to control the local oscillator frequencies corresponding to the channels, with one output of the multivibrator corresponding to the priority channel. A low-frequency free-running oscillator and a pair of monostable delay circuits, having a relatively short time interval, produce pulses to change the state of the multivibrator. With no signals being detected on any of the channels, the multivibrator is controlled by the monostable delay circuits to provide a relatively rapid sequential scanning of the channels. Detection of a carrier on a nonpriority channel, however, shifts control of the bistable multivibrator to the free-running oscillator to reset the bistable multivibrator to scan the priority channel, whereupon control is returned to the monostable circuits. Provision is made for attenuating the audio output whenever a nonpriority channel is being received and for increasing the sensitivity of the squelch circuit whenever a nonpriority channel is being scanned.

公开(公告)号：US3702440A

公开(公告)日：1972-11-07

申请号：US3702440D

申请日：1970-11-16

Applicant: MOTOROLA INC

Inventor： MOORE GEORGE G

IPC: H04W88/18 ,  H04B1/16

CPC classification number: H04W88/188

Abstract: The selective calling system includes a transmitter having first and second signal generators providing sinusoidal and rectangular signals which are combined to form a modulated calling signal. Each receiver of the system includes a first demodulator which demodulates the modulated calling signal and a second demodulator which demodulates the rectangular signal. A frequency selective device connects the first demodulator to a first input of an AND gate and a repetition rate selective device connects the second demodulator to a second input of the AND gate. If the demodulated frequency and repetition rate are within the passbands of the devices, the AND gate provides a turn-on signal which allows primary information to be reproduced by the receiver. The system can be modified so that auxiliary information is transferred to the receivers by the calling signal.

Abstract translation: 选择呼叫系统包括具有第一和第二信号发生器的发射机，其提供正弦和矩形信号，其被组合以形成调制的呼叫信号。 系统的每个接收机包括解调调制的呼叫信号的第一解调器和解调矩形信号的第二解调器。 频率选择装置将第一解调器连接到与门的第一输入，并且重复频率选择装置将第二解调器连接到与门的第二输入。 如果解调的频率和重复率在设备的通带内，则与门提供允许主信息由接收机再现的导通信号。 可以修改系统，使辅助信息通过呼叫信号传送到接收机。