Abstract: A phase detector circuit which compensates for unwanted variations induced in an input signal by the operation of a thresholding input circuit such as a frequency divider. The circuit monitors the level of a supply voltage used by the input circuit to provide a supply variation signal indicative of such unwanted variations. The supply variation signal is then used to correct the output of the input circuit. In one embodiment that compensates for noise in the output of a digital frequency divider used as an input circuit in a high frequency phase detector, a high-pass filter and amplifier detect the supply variations. The supply variation signal is then fed to a phase adjustment circuit which compensates for the variations in supply voltage by adjusting the conduction threshold of a differential transistor pair. A variable impedance can be arranged to optimally attenuate the supply variation signal, thereby obtaining maximum noise elimination at a given operation frequency.

Abstract: Power for an r.f. oscillator/modulator located at the antenna input terminals of a television receiver is derived from synchronization signals generated remotely from the receiver and applied to the r.f. oscillator/modulator via a cable.

Abstract: An address tone decoder is disclosed for detecting a predetermined address tone code and for activating remaining pager circuitry upon receipt of the appropriate address tone sequence in which the detection of tones of the appropriate frequencies starts normally-off timing circuits. The signal from the timing circuit associated with the first tone is effectively elongated to coincide with the signal from the timing circuit associated with the second tone in the sequence. A cross inhibiting circuit provides shock protection by resetting the timing circuit associated with one tone when another tone is simultaneously present. A group call timer is included which provides an activation signal responsive to an elongated first tone.

Abstract: A hand held pager is disclosed which displays a transmitted message in hard copy form on a tape to permit a written record of the message for readout at the convenience of the recipient of the message. The hard copy pager is provided with a printing system in which the printing medium is continually moved past the printing head without significant degradation of the information recorded so that indexing of either the head or the printing medium is avoided. In one embodiment, the pager package includes a cover which is slipped over the main body of the package for providing part of the tape threading channel, with at least a portion of the sliding cover being transparent so that characters imprinted on the tape are readily visible through the cover. Also in this embodiment, a unique address and group call decoder includes a number of normally-off timer decoding elements which are actuated upon receipt of a decoded tone and are cross-inhibited to provide improved shock protection.