Abstract: The mobile radio system includes a plurality of power amplifier modules having discrete power levels, a common transceiver module and a plurality of control head modules having different control functions. Selected ones of the power amplifiers and control heads are electrically and mechanically coupled to opposite ends of the transceiver. In one form, the control head may be remotely mounted and electrically coupled to the selected power amplifier. A common bracket is used to mount a radio having selected ones of the power amplifiers coupled to the transceiver with a selected control head. In a further embodiment, a receptacle having electrical fittings at its rear end and an opening at its opposite end receives the radio through its open end with the electrical connections being automatically coupled to one another upon final seating of the radio in the receptacle. The radio includes a handle which forms a latch for releasably securing the radio in the receptacle.

Abstract: A computer-controlled portable radio communications device has RF and audio circuits controlled by a programmed computer in accordance with a predetermined modus operandi and includes an externally accessible multi-point electrical connector having input/output connections which communicate with the programmed computer. The computer is programmed to monitor the electrical impedance externally connected to at least one contact point of the connector and to alter the modus operandi of the portable radio system in response to such monitoring. In the exemplary embodiment, each of plural different types of accessory devices include a predetermined electrical impedance uniquely corresponding to that particular accessory device. The circuits are arranged so that no damage can be inflicted by accidental external electrical short circuits which the user may accidentally cause.

Abstract: A circuit that determines which channels of a radio receiver are to be scanned and which channels are to be skipped is programmed or preset by a first switch which selectively energizes an automatic search circuit or a manual channel selector switch and a scan-skip switch. When the channel selector switch is energized, individual channels can be selected. As each channel is selected, a readout circuit provides an indication if the channel has been previously programmed to be scanned, but provides no indication if the channel has been previously programmed to be skipped. Also, each channel selected by the channel selector switch can be programmed for scanning or skipping by the scan-skip switch. The circuit permits a large number of channels to be programmed by only three switches, thus saving space which is limited in very small radio receivers.

Abstract: A search circuit is provided for sequentially activating selected local oscillators to cause a radio receiver to receive the radio frequency channel corresponding to the frequency of the activated local oscillator. The search circuit provides repetitive pulses which are passed through a skip circuit and are then decoded in sequence. The decoded signals are applied to respective local oscillators and are also applied to respective memory circuits. Each memory circuit can be preset with a scan or a skip memory signal. If preset with a scan memory signal, a memory circuit produces a constant scan output. If preset with a skip memory signal, a memory circuit produces a skip output each time it receives its respective decoder signal. All of the memory circuit outputs are applied to the skip circuit. Each memory circuit which produces a scan output causes the skip circuit to pass the repetitive pulses through without change.

Abstract: A radio receiver is provided with a local oscillator whose frequency is switched so that the receiver is normally receptive to the stronger signal but so that the receiver is momentarily and periodically made receptive to the other weaker signal. A circuit compares the relative strengths of the two signals, and if the weaker signal becomes stronger than the previously stronger signal, then reception is switched to the now stronger signal with momentary and periodic reception of the now weaker signal. Thus, interference-free and good reception of the transmitted information is provided.