206
by ±4.5 kHz. Positive deviation indicates a binary zero and negative
deviation a binary one.
In America the Golay sequential code is widely used for paging
addressing. The format for tone-only paging consists of 12 address
bits followed by 11 parity bits for each 23 bit word. Two bit rates
are used, 300 bit/s for address codewords and 600 bit/s for message
codewords.
There are European paging and message systems in operation
including Euromessage and the frequency agile European Radio Mes-
sage Service (ERMES).
18.2 Cordless telephones
CT1
The first generation of cordless telephone, still very popular in the
UK, is designed to serve the domestic environment with a range of
100 m. The base station transmits on one of eight frequencies between
1.6 MHz