Abstract: A station selecting system for use in a multi-channel communication system having a plurality of display devices respectively corresponding to the communication channel. Circuitry is provided for placing the system in a monitor mode of operation where all channels are scanned once to determine which ones are available for communication, the latter channels being indicated by actuation of the display devices respectively corresponding thereto. Circuitry is also provided for placing the system in an autoscan mode of operation where the channels are sequentially scanned until a channel available for communication is located, at which time scanning ceases and the selected channel is indicated by the actuation of its corresponding display device.

Abstract: An oscillator suitable for use as a local oscillator of high frequency apparatus comprises a voltage controlled oscillator, a reference oscillator, a phase detector for detecting the phase difference between the oscillation frequencies of the voltage controlled oscillator and the reference oscillator, means for filtering the output of the phase detector to produce a DC voltage and a phase synchronizing loop for feeding back the DC output of the low-pass filter means to the voltage controlled oscillator. Depending upon whether the oscillation frequency of the reference oscillator is maintained at a duty cycle of 50% or at a value other than 50%, the oscillation frequency of the voltage controlled oscillator is synchronized with an odd multiple or an integer multiple of the oscillation frequency of the reference oscillator when the oscillation frequency of the voltage controlled oscillator is varied forcibly.

Abstract: A multi-channel communication system including automatic station selecting circuitry and circuitry for preventing actuation of the station selection circuitry by noise or the like. The station selecting circuitry automatically, sequentially generates a plurality of local oscillator signals which are mixed with incoming information signals transmitted in one or more of the channels of the system. Whenever the frequency difference between an information signal and a local oscillator signal falls within the pass band of the receiving channel, a sensing signal is generated which stops the automatic station selector so that communications can occur on the selected channel. Circuitry is also employed to discriminate between noise and an appropriate information signal in the receiving channel so that the above-mentioned sensing signals are generated only when information signals are present.

Abstract: In a method of presetting a receiver of the synthesizing type wherein the ratio of frequency division of a frequency divider in a phase locked loop is set in accordance with the content of an up-down counter, a search signal and a write signal are generated for sweeping the up-down counter, the contents of the up-down counter are sequentially written in a memory device each time an intermediate frequency output is obtained, and the up-down counter is preset in accordance with a data read out of the memory device thereby enabling the receiver to receive the signal from a desired broadcasting station.

Abstract: An automatic return apparatus for the pick-up arm of a record player including a cam plate for lowering the pick-up arm at the beginning of playback and for returning the arm at the end thereof. A crossed cam is rotatably mounted on the plate to engage the pick-up arm when it is being returned to its rest position and effect disengagement thereof at all other times. A four-armed lever for effecting various functions such as holding the cam plate in position during playback, actuating a muting switch during the return of the pick-up arm to its rest position, initiating the return of the pick-up arm return and resetting the apparatus for the next return of the pick-up arm is also provided.

Abstract: A trigger signal for indicating the receiving point of a synthesizing type high frequency receiver including a voltage controlled oscillator is detected by a circuit comprising means for deriving an intermediate frequency signal from the received high frequency signal, a wave shaper for shaping the waveform of the intermediate frequency signal, a first monostable circuit connected to the output of the wave shaper and having a time constant larger than the width of the output but smaller than the minimum frequency spacing between individual stations, a second monostable circuit connected to the output of the first monostable circuit and having a time constant smaller than the width of the output of the wave shaper, and an AND gate circuit for producing a logical product of the output of the second monostable circuit and a sweeping clock signal.