公开(公告)号：US3731200A

公开(公告)日：1973-05-01

申请号：US3731200D

申请日：1972-02-22

申请人： MOTOROLA INC

发明人： SCHWENDEMAN R ,  D AMICO T ,  PETRAKOS N

IPC分类号： H04W88/18 ,  H04B1/00

CPC分类号： H04W88/188

摘要： A paging system includes a transmitter for transmitting a carrier frequency signal modulated by subaudible tone signals in response to audible tone signals coupled to the transmitter from a remote point. An encoder at the remote point develops the audible tone signals which are coupled to the transmitter over standard telephone channels. At the transmitter, a circuit converts the audible tone signals to first square wave signals having the same frequency as the audible tone signals. A divider circuit divides the first square wave signals by a particular number to develop second square wave signals having the same frequency as the desired subaudible tone signals. The second square wave signals are coupled to a low pass filter which attenuates all frequencies above the subaudible tone signal frequencies and develops a sine wave having the desired subaudible tone frequency. A frequency selector circuit may also be employed and is coupled to the divider circuit. The frequency selector circuit is operative to select the second square wave signals having a frequency above a predetermined frequency and couple them to a first filter; and is further operative to select the second square wave signals having a frequency below a predetermined frequency and couple them to a second filter. The first and second filters have low pass attenuation characteristics and are operative to filter the square wave signals coupled thereto and develop the particular subaudible tone signals therefrom for modulating the transmitter RF carrier.

摘要翻译： 寻呼系统包括发射机，用于响应于从远程点耦合到发射机的可听到的音调信号，发送由无法听到的音调信号调制的载波频率信号。 在远程点处的编码器产生通过标准电话信道耦合到发射机的可听音信号。 在发射机处，电路将可听音信号转换成具有与可听音音频信号相同频率的第一方波信号。 分频器电路将第一方波信号除以特定数字，以产生具有与期望的低音音调信号相同频率的第二方波信号。 第二方波信号耦合到低通滤波器，该低通滤波器衰减低于次要音调信号频率的所有频率，并产生具有所需听觉音调频率的正弦波。

公开(公告)号：US3798545A

公开(公告)日：1974-03-19

申请号：US3798545D

申请日：1972-02-07

申请人： MOTOROLA INC

发明人： SCHULTZ N ,  SCHWENDEMAN R

IPC分类号： H04B1/40 ,  H04W88/18 ,  H04B5/04

CPC分类号： H04W88/188

摘要： A high capacity paging system includes a transmitter for transmitting a modulated signal in response to a message including address signals followed by audio signals. Each transmission is initiated by actuating the switch and terminated by deactuating the switch. Control circuitry is operative in response to the switch actuation to actuate the transmitter. The control circuitry includes time delay circuitry for holding the control circuitry operative for a first predetermined time period after deactuation of the switch. Address circuitry develops the address signals and is operative in response to actuation of the switch to couple the address signals to the transmitter for a second predetermined time period no greater than the first predetermined time period. Audio delay circuitry is operative in response to operation of the control circuitry to delay audio signals coupled from a microphone by the first predetermined time period and couple the delayed audio signals to the transmitter for transmission thereby. The address signals of the succeeding message are transmitted simultaneously with the terminal portion of the audio signals in the preceding message.

摘要翻译： 高容量寻呼系统包括用于响应于包括跟随音频信号的地址信号的消息来发送调制信号的发射机。 每个传输通过启动开关启动，并通过停用开关来终止。 响应于开关致动以控制发射器，控制电路是可操作的。 控制电路包括时间延迟电路，用于在开关停用之后保持控制电路在第一预定时间段内操作。 地址电路产生地址信号，并且响应于开关的致动而工作，以将地址信号耦合到发射机在不大于第一预定时间段的第二预定时间段内。 音频延迟电路响应于控制电路的操作而工作，以将从麦克风耦合的音频信号延迟第一预定时间段，并且将延迟的音频信号耦合到发射机以便传输。 后续消息的地址信号与先前消息中的音频信号的终端部分同时发送。