Abstract: A local oscillator for a radio receiver includes a voltage controlled oscillator (VCO), a decoder and controller for providing a control voltage to the VCO, an error detector circuit for detecting an error in the frequency of the VCO on the basis of a received signal processed with the oscillating signal from the VCO, a temperature probe and a memory. The local oscillator is initially set up during manufacture by detecting any errors in the frequency at selected temperatures, and storing data in the memory indicative of the control voltage required to compensate for the frequency error for each temperature. In operation the decoder and controller applies the appropriate control voltage to the VCO on the basis of the data stored in the memory relative to the temperature detected by the temperature probe.

Abstract: In a decoder suitable for use in a paging receiver of the type responsive to a transmission which includes a preamble sequence followed by batches each containing a synchronization word followed by a plurality of address and/or message words, the decoder is operative to detect a single synchronization word. Thereafter, the decoder is powered up to search in its specific frame in each batch by means of a clock which has been synchronized with the transmission and which provides the timing for searching in the specific frame of all subsequent batches.The clock may have coarse and fine modes of timing control, the coarse mode being applicable when initial bit synchronization is being attained, and the fine mode being applied subsequently to reduce the risk of the clock drifting out of synchronization.

Abstract: An FM demodulator includes frequency conversion means (20) to derive from an FM input signal (10) a pair of like signals that are mutually phase-displaced by 90.degree.. Such signals are filtered (26,28), squared (30,32) and sampled (38). The output signal (40) of the sampling means (38) is used to control (62) the local oscillator (16) of the frequency conversion means (20). In one arrangement, the magnitude of the control applied to the oscillator (16) is dependent on the frequency of one of the squared (30) signals, whereas the direction is dependent on the logic state of the output signal (40). A similar control method can be applied to a superheterodyne receiver.