Abstract: In a cellular radio system having a two layer cell structure comprised by macrocells (1) overlaying microcells (2), handover occurs only via the macrocell layer. Thus when the quality of a call handled by a microcell (2) deteriorates below predetermined criteria the call is handed up rapidly to the umbrella macrocell and is only handed back down to a microcell when the handset has been in that microcell for a predetermined time and the quality of the link thereto exceeds predefined criteria.

Abstract: In a cellular radio system including a plurality of cells (e.g. cell sectors or micro cells) (4, 5, 8, 9, 10, 11) each normally using a respective channel for interference reduction purposes, a number of the cells are arranged in groups (6) and in the event of a cell associated with equipment moving within a group (6), all cells (4, 5, 8, 9, 10, 11) of that group use a common channel whereby to facilitate handover between them.

Abstract: A fractional-N frequency synthesizer having a programmable divider and a control circuit therefor, wherein said control circuit incorporates a digital delta-sigma modulator operating as an interpolator.

Abstract: For both recording and replay, a digital audio tape (14) is accelerated very rapidly by a motor servo (9), motor (8) and capstan (7) so that the tape speed overshoots nominal speed range before settling back to this range in an oscillatory manner. The digital samples are recorded and replayed via a head (15), a random access memory (16) and input/output electronics (19). During recording, the store (17) is precharged by starting to write in as soon as acceleration is initiated. Read-out to the tape is initiated as soon as the tape first reaches the nominal speed range. Uniformity of samples as recorded on the tape is preserved by clocking a read address generator (21) at a rate proportional to tape speed, signaled by a tachometer (7). The write address generator is clocked at the constant sampling rate. For replay the write address generator is clocked at the tape speed rate while the read address generator (21) is clocked at the constant sample rate.

Abstract: In producing an edited tape (31) the lead-in material up to a first edit point is separated from the lead-out material running from a second edit point by a space containing unwanted material and accommodating the actual or notional splice. The unwanted material ensures correct operation of error protection for all of the wanted material on replay. The first and second edit points are marked by codes placed on the tape (31) by a code processor (43) and supplementary head (42). During replay the digital data recovered from the tape by a head (32) is entered into a random access buffer store (34) under control of a write address generator (38) and read out to output electronics (37) under control of a read address generator (39) running at the audio sampling rate.

Abstract: A multitrack tape recorder records and replays digital data on a plurality of data tracks (15) by way of record/replay electronics (7), a record head (5) and a replay head (6). Channels (8) corresponding to the tape track (15) are provided for input to and output from the electronics (7). An additional channel (11) carries auxiliary data related to the signals in the channels (8). This data is formatted during recording by the electronics (7) into a block format compatible with the data format on channels (15) and is recorded on a separate dedicated track (16). The auxiliary information may be formatted in labels each of which has an instruction field and a parameter field. The labels can carry a wide variety of information relating to operation of the system. As one example, a label may contain in the instruction field an instruction to increase the playback gain by an amount contained in the parameter field.