oth the handset and base unit. 72 bits (1ms) (one burst) 66 bits D channel Preamble CHM or SYNC word D channel 16 bits 10 bits 24 bits 16 bits Dead time Dead time 6 bits 6 bits Receive Transmit Receive Figure 49.6 Format used for multiplexer 2 of Figure 49.5 49/8 Cordless telecommunications For interworking with digital networks the requirements of ETSI required. From a speech transmission point of view the moderate draft recommendation NET33 are met. In the case of analogue processing delays involved do not require echo control circuitry or network interconnection, for historical reasons, the requirements raise absolute network delay issues. With these benefits the radio change from country to country throughout Europe. So to ensure a circuit design is simplified and the complexity of implementation is common handset specification, particularly for telepoint applica- concentrated at baseband which can made using low power con- tion, any necessary country specific corrections to the overall sumption, large scale integration CMOS technology. speech transmission characteristic is built in to the base unit. To Figure 49.7 is an example of the degree of integration that is avoid problems arising from terminal speech echo in the trans- possible and which leads towards a common set of components to mission network the loop delay imposed on a CT2/CAI link has support all applications. This is a key objective in realising the been set to less than 5ms. benefits of large volume production in terms of minimised compo- The digital speech codec algorithm used by CT2/CAI has been nent costs. taken from the CCITT Recommendation G.721 (Blue Book) which defines a 32kbit/s adaptive differential pulse code modulation codec. Some, strictly controlled, licence is given to manufacturers to simplify the resulting codec in order to limit power requirements 49.4 DECT digital specification and complexity. Around the mid 1980's a number of companies under the auspices 49.3.5 Implementation of the European Conference of Telecommunications 