traffic information (I) and Peak transmit power 250mW offers 320 bits per burst which is equivalent to 32kbit/s. The four X Modulation Gaussian FSK (B.T. = c0.5) bits (which optionally can be extended to eight) are provided to detect collisions between bursts emanating from independent, and Nominal peak deviation 288kHz hence un-synchronised, systems. It should be noted of course that Duplex channels per frame other multiplex structures are used in DECT particularly in the channel set up phase. Frame period System loop delay c25ms 49.4.7 Transmission plan and digital codec Bits per timeslot Bits per burst DECT is subject to the same constraints as applied to CT2/CAI in terms of transmission performance. It is notable that both use the Guard time bits same codec standard and hence offer the same basic speech quality Net channel rates (traffic) 32kbit/s per slot (B field) level. However, since DECT employs TDMA working the inevit- able consequence is that DECT loop delay amounts to about 25ms. Such a delay cannot be tolerated in the local public network in the presence of speech echoes from the DECT handset. At present two approaches are being taken towards the amelioration of this effect: Antenna diversity located at the base station is considered the first line of defence in such instances. By designing handset with virtually zero echo return. This calls for high orders of acoustic coupling loss between handset ear 49.4.5 Radio operational features and mouth pieces approaching 46dB. A combination of good handset design combined with the use The fixed part (FP) has an active channel for paging and synchroni- of acoustic echo cancellation or control. sation. An incoming call is paged on all FP and the PP responds on a channel chosen by the PP. The latter seems to be preferred. Unfortunately the problem of If channel quality deteriorates, PP moves out of range or due to echo cancellation and control in terminal equipment is not an increased interference, then handover is initiated to a more appro- independent design