Abstract: A Computerized Mobile Two-Way Radio System is provided having microprocessor enhanced capabilities and versatility for wide area/multiple region two-way radio networks with multiple categories of users and adaptability to multiple international standards and mobile radio equipment configurations. The main elements of the system consist of (1) a microprocessor-based Control Unit, (2) a Digital Serial Interface/Link and (3) a microprocessor-based Convertible Transceiver Unit. The Control Unit provides many facilities and capabilities for the operator and the system in compact form. The Interface/Link provides a two-way path for serial data consisting of digitized audio and digital command and status signals. The Transceiver Unit is designed for operation and control over the Digital Serial Interface/Link.

Abstract: A digital serial interface system is provided for communicating digital signals including digitized audio between microprocessor-based Control and Transceiver Units of two-way radio communications equipment. The system of the invention essentially comprises three subsystems: (1) an interface in the microprocessor-based Control Unit, (2) an interface in the microprocessor-based Transceiver Unit and (3) a two-way medium for linking the two units. Various signals and audio in the Control Unit interact with a software-driven microprocessor of the Control Unit and are digitized and then translated into a serial format, organized in channel groups through a TDM (Time Division Multiplex)/PCM (Pulse Code Modulation) process and transmitted in frames through a two-way medium to the Transceiver Unit which is also microprocessor-based and incorporates a similar interface. The digital data communicated to the Transceiver Unit then undergoes a reverse process. The Interface System is duplex (bidirectional).

Abstract: A method for scrambling speech such as in a mobile land based communication system is disclosed. Essentially, variable length time samples of digitized speech are stored and time inversion scrambled. The scrambled speech is converted back to analog form and transmitted to a receiver which reciprocates the process to reproduce the desired speech signals. Scrambling and descrambling of the speech signal is synchronized to provide corresponding sample time inversions and accurate reproduction of the speech input signal. The level of security afforded by the scrambling method may be varied by varying the length of the sampling period or by mixing forward and reverse time samples under control of an algorithm.

Abstract: A control system for microprocessor and software enhanced land mobile radio communications systems is provided to increase versatility, capabilities and facilities while providing an easier and more precise control of various radio protocols. As the usage of microprocessors and software is increased in radio communications equipment, additional capabilities, digital protocols and versatility can be desired in such equipment. However, this requires additional and special controls and prior art approaches have limitations with respect to capacity, versatility, size and compatibility with digital protocols. The innovative approach of the invention provides a compact new system to replace prior art multipositional knobs and switches and refines the system of control. The novel control system provides for an efficient utilization of space while achieving outstanding versatility and new operational and control capabilities.

Abstract: A method and apparatus for filling audio blanks in a message received by a receiver resulting from switching the receiver between a plurality of input channels each having a different message for selecting the channel of highest priority is disclosed. A recording and playback device is connected between the receiver and an output channel for recording a given time segment portion of a first message. The receiver is switched to a second channel for a period of time equal to the given time segment for receiving a second message and for determining which channel has a higher priority. The recorded portion of the first message is delivered to the output channel simultaneously with the switching of the receiver to the second channel to repeat the first message portion at the output channel, thereby to fill in the audio blank resulting from switching the receiver between the input channels.

Abstract: A combined phase and frequency modulation device for modulating a data signal in order to generate a plurality of narrow band signals for a communication system is disclosed, characterized by a direct synthesis phase locked loop for generating an output data signal having a selected frequency, a signal divider and phase modulator circuit, and a frequency multiplier for multiplying a modulated signal to produce an output having a desired frequency. The signal divider and phase modulator circuit includes a frequency divider which produces two quadrature related signals from the output data signal. A modulator connected with the frequency divider generates a suppressed carrier double sideband signal from one of the quadrature related signals. A summing device connected with the frequency divider and with the modulator combines the carrier signal with the other quadrature related signal to produce the modulated output signal which is multiplied by the frequency multiplier.