A cordless phone 1 is able to communicate signals 3 via antenna 2 and 3 with transponder unit 5. When the transponder 5 is physically connected (as shown) via multi-way connector 12 to base station 19, the system communicates via PSTN interface 9 and cable 10 connected to local-loop socket 11 within a fixed telephone network. When the transponder 5 is disconnected (not shown) from base station 19, the system communicates via external antenna 6 by radio link with a local base station within a cellular phone network. The base station 19 provides means to recharge the batteries (not shown) of cordless phone 1 via connectors 13 and transponder unit 5 via connectors 14, with dc supply being provided by power plug 16 via cable 17. The transponder unit may include a display screen and PDA electronics (not shown), or, be incorporated within a portable computer (not shown).