Abstract: A frequency shift keyed (FSK) generator producing an output frequency which is determined by gating through a selected one of a plurality of crystal controlled oscillators. The oscillator output is divided by a digital frequency divider to the operating tone frequency. The square wave output of the divider is filtered to a sinewave by an active tracking bandpass filter which is instantaneously switched to the operating frequency simultaneously with the selection of the appropriate crystal controlled oscillator.

Abstract: A crystal test set comprising an oscillator circuit in which a crystal under test is an integral part. The resistor substitution technique is employed in which the crystal and a variable resistor are alternately connected into the oscillator circuit. With the resistor in the circuit, the circuit is tuned to the resonance frequency of the crystal. The value of the resistor is adjusted to produce a voltage across the resistor equal to the voltage across the crystal. The adjusted value of the resistor is measured and corresponds to the crystal impedance. A measuring circuit, responsive to the voltage drop across the crystal, provides a direct measure of the crystal power dissipation.

Abstract: A high speed arrangement for simultaneously demodulating the AM and FM information coming in on a tone frequency carrier. In the case of the incoming tone signal being only FM modulated, the FM demodulator extracts the data whereas the AM demodulator provides an output which can be used to squelch the FM demodulated data channel when noise or interference reaches a predetermined level.