Abstract: A receiving apparatus has a clock frequency generating circuit comprising in a first embodiment a low cost oscillator whose frequency is higher than the wanted clock frequency and in a second embodiment a low cost oscillator whose frequency can be higher or lower than the wanted clock frequency. By means of subtracting pulses from (first embodiment) or adding/subtracting pulses (second embodiment) to/from the output of the low cost oscillator, a clock frequency is generated which is stable within a specified tolerance range.

Abstract: A method of, and system for, communicating s-bit symbols using an M-ary modulation scheme in which a plurality of code words are arranged as rows of a block which is read-out orthogonally to the rows. In order to increase the dependability of the recovered code words, when the code words are stored or read-out the order of the bits forming some of the s-bit symbols is transformed so that those which would have been least significant bits (LSBs) are most significant bits (MSBs) and vice versa, the MSBs being affected less by noise than the LSBs when transmitted. At the receiver those s-bit symbols which have been transformed are restored to their original order.

Abstract: A method of fade recovery in a digital message transmission system in which data is encoded into code words, formatted into frames of a batch and transmitted in accordance with one or more transmission formats, and a synchronization code word, indicative of the transmission format, is inserted at the beginning of each batch, the method of fade recovery including energizing a receiver for a first predetermined time period and storing any signals received during the first predetermined time period, analyzing the stored signals to determine if the stored signals being transmitted is in one of the transmission formats, and if so, maintaining energization of the receiver in predetermined time increments for up to a maximum of a second predetermined time period and checking if any of the stored signals associated with each such time increment conform to at least one of the transmission formats.