Abstract: A voltage controlled oscillator (VCO) and reference oscillator are connected in a phase locked loop with a first phase detector, loop switch, and acquisition sawtooth sweep circuit. A second phase detector and fast integrator circuit are connected to the VCO and reference oscillator in quadrature relation with respect to the first phase detector. As the acquisition sweep circuit sweeps the VCO, the fast integrator produces a signal whose magnitude increases as the swept VCO frequency approaches the frequency needed for the phase locked loop to achieve phase lock. When this signal magnitude exceeds a predetermined threshold, an output control signal is produced. This output control signal causes the loop switch to close and make the phase locked loop operational. A delay circuit is connected to the second phase detector and fast integrator. The delay circuit produces a delayed output at a predetermined time after the control signal is produced.

Abstract: An arrangement for interconnecting a pair of hybrid integrated circuit boards mounted by means of pins in an upstanding position on a horizontally extending base circuit board in closely spaced, substantially parallel relationship, each of the hybrid circuit boards being provided with a row of contact terminals extending along the upper edge thereof together with a secondary printed circuit board having a row of downwardly directed, spring-like contact elements mounted along each side edge, the contact elements beng spaced so as to correspond with the contact terminals on the hybrid boards and with oppositely disposed contact elements being interconnected by a conductor whereby the secondary board may be detachably mounted in a horizontally extending position across the upper edges of the hybrid boards with the contact elements in each row in circuit making engagement with the adjacent contact terminals on the underlying hybrid boards thereby interconnecting the printed circuits of the hybrid boards.

Abstract: Remote equipment is controlled from each of several control locations by means of an arrangement which prevents more than one control location from producing a control signal at the same time and which provides a delay between control signals for proper resetting of the controlled equipment. The response of the arrangment is optimum in that the effective delay is never greater than the minimum required for proper control of the remote equipment. The control locations may also be provided with logic circuits connected together so that each control location has the desired priority of control with respect to the other control locations.

Abstract: A container type structure for providing a radio frequency shield is described having an integral latching means for securing a cover on the container, which latching means can readily be operated to allow the cover to be removed. The latching means are formed from a tongue-like member extending substantially parallel of the surfaces of the side walls of the container and resiliently biased in a direction for engagement with appropriate apertures or receptacles on the cover. Slots are provided through which the latch can be manipulated to allow ready removal of the cover.

Abstract: A battery charger for a portable radio having a battery pack forming a radio-battery unit and arranged to accommodate various combinations of both radio and battery lengths, the charger being provided with a recess for positioning a radio-battery unit in a selected axial position therein with a plurality of axially spaced sets of charging contacts disposed within the recess, each set being arranged for selective circuit making engagement with charging terminals on the battery pack in accordance with the length of the radio inserted with the charger recess.

Abstract: An easily assembled battery contact arrangement for a radio is formed of mating parts which can be assembled without tools and fitted into a mating receptacle in the radio. This arrangement includes an opening which accepts the terminal of a chargeable battery, and provides electrical connection to an external projection which permits the battery to be charged while the battery is in the radio.

Abstract: A solid state device, such as a power transistor, is fastened to a mounting arrangement that provides good heat conduction to a chassis or heat sink, that holds the solid state device so that its leads can be connected to a printed circuit board without strain, and that occupies a relatively small area of the printed circuit board.

Abstract: A housing for a two-way radio is formed of front and rear covers, left and right sides, a base plate, and a top control panel and cover. Certain pieces are provided with corresponding mating surfaces to aid in assembly, and the pieces are held together by screws and nuts. Selected pieces may be substituted to permit variations in internal structure and to provide different configurations without the need to change all of the other pieces.

Abstract: A multifrequency generator is provided for a radio transmitter and receiver that must operate on a plurality of channels. The generator includes a channel synthesizer having a phase-locked loop that provides a respective output frequency signal for each selected channel. The generator includes a transmitter synthesizer connected to the channel synthesizer and having a phase-locked loop and a mixer that provide the transmitter synthesizer output signal. The generator includes a receiver synthesizer connected to the channel synthesizer and having a phase-locked loop and a mixer that provide the receiver synthesizer output signal. The frequency of the channel synthesizer output frequency is selected to be substantially lower than the transmitter and receiver synthesizer output frequencies to reduce the noise sideband components of the transmitter and receiver output signals.

Abstract: Received power line trip signals are delayed in their tripping function by a circuit which causes introduction of the delay in response to a wideband received signal rising rapidly above a dynamic amplitude level, or in response to a narrowband received signal going outside upper and lower amplitude limits. Either condition could indicate a false trip signal, so that a delay before actual tripping is desirable.

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: The prior art tone detector shown in U.S. Pat. No. 3,962,645 provides a repetitive sequence of vector signals at a predetermined or selected rate determined by the desired tone frequency to be detected. Each vector in the sequence has a different phase or angular direction. One vector in each sequence is selected at a time corresponding to a selected (usually zero) point in each cycle of received tone frequency. If the sum of a number of selected vectors exceeds a threshold, an indication of the desired tone is provided.In some tone detectors a phase shift in the tone can indicate a selected condition. Such a phase shift is detected by counting the number of vectors which are produced after the phase shift, whose magnitude added to the magnitude of the vectors produced before the phase shift exceeds a threshold, and whose sign differs from the sign of the vectors produced before the phase shift. When the count reaches a predetermined number, a phase shift indication is provided.

Abstract: A plurality of circuits are provided for responding to various conditions in a radio receiver. Each of the circuits produces a first signal in response to the presence of its respective condition and produces a second signal in the absence of its respective condition. Each circuit removably engages a respective receptacle which is arranged to produce the first signal if its circuit is removed. A plurality of first logic gates have their inputs connected to the circuits in a predetermined arrangement. Each first gate produces a third signal in response to all of its inputs having first signals applied thereto, and produces a fourth signal in response to any one of its inputs having a second signal applied thereto. An output logic gate is connected to the first logic gates. The output gate produces an unsquelch signal in response to at least one third signal produced by a first gate, and produces a squelch signal in response to all of the first gates producing fourth signals.

Abstract: A radio transmitter power amplifier is connected to a driver circuit whose drive power determines the output power of the power amplifier. Direct current is supplied to the driver circuit under the control of a temperature control circuit which compares a temperature indicative voltage with a voltage indicative of the direct current drawn by the power amplifier. If the power amplifier direct current is above a desired level for a given temperature, the control circuit reduces the direct current supplied to the driver circuit, and hence reduces the output power of the power amplifier. If the power amplifier direct current is below a desired level for a given temperature, the control circuit increases the direct current supplied to the driver circuit, and hence increases the output power of the power amplifier.

Abstract: Frequency-shift-keyed signals are detected by a receiver having an input which supplies the received signals to first and second mixers. A local oscillator produces signals at a frequency midway between the two frequencies of the frequency-shift-keyed signals. The oscillator signals are supplied to the first mixer at a first phase angle (sine), and are supplied to the second mixer at a second phase angle (cosine) displaced 90 degrees with respect to the first phase angle. The first mixer output is applied to a first lowpass filter which removes the high frequency (or sum) signals and passes only the low frequency (or difference) signals. The second mixer output is applied to a second lowpass filter which also removes the high frequency (or sum) signals and passes the low frequency (or difference) signals. The first filter signals are applied to a first 90 degree phase shifter, and the second filter signals are applied to a second 90 degrees phase shifter.

Abstract: Some radio repeaters receive a voice signal on a first frequency and an information tone signal on a second frequency, and transmit both the voice and tone signals on a third frequency. A circuit is provided to sense the presence of the tone signal and to filter that frequency from the voice signal and also attenuate the remainder of the voice frequencies. The filter prevents the voice signal from interfering with the tone signal, and the attenuator prevents the transmitter modulator from being overloaded, thus providing improved repeater transmission of the tone frequency.

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: The relative frequency of two signals is indicated by applying pulses indicative of the two signals to respective bistable flip-flops. The flip-flops are interconnected to produce two binary outputs each of which varies between two binary values in response to occurrence of the pulses. These binary outputs are applied to a logic circuit which produces a binary output that varies between two binary values as a function of the similarity and difference in binary values of the two flip-flop signals. The binary output of the logic circuit is applied to two further bistable flip-flops along with the pulses to control the outputs of the further flip-flops. The outputs of the further flip-flops produce respective signals which indicate the relative frequency of the two signals, and which can be used to change this relative frequency.

Abstract: A radio frequency power amplifier is frequently provided with a feedback circuit to maintain the output power of the amplifier at a predetermined level. When the load connected to the amplifier changes, the feedback circuit causes the amplifier to produce the amount of power needed to maintain the predetermined level of power. If additional power is produced, it may be large enough to damage or destroy the amplifier and other circuits. A protection circuit is provided to prevent this. The protection circuit uses a differential amplifier having a first input provided by an output power sensor, a second input provided by a reference voltage, and an output for controlling the supply power to the radio frequency power amplifier. The two inputs are adjusted so that the differential amplifier becomes saturated when the sensed output radio frequency power is at some selected safe level above the normal output power level.

Abstract: Crystal oscillators have been provided with a voltage sensitive capacitor or varactor which can be varied to improve the frequency stability of the oscillator over the desired range of temperature. A temperature compensator is provided for varying the voltage applied to the voltage sensitive capacitor as a function of temperature. The temperature compensator has a middle temperature range circuit, a cold temperature range circuit, and a hot temperature range circuit. The compensator can be constructed as an integrated circuit with external resistors which can be varied (or trimmed), and provides compensating voltages that stabilize the oscillator frequency over a wide range of temperatures.