Letter: Who's calling?

Sir: There is a solution to Emma Jones's problem with calling line identification (letter, 19 December). If one does not want one's telephone to ring unless the caller's identity is given - which is also my preference - it is possible with modern digital technology to give the caller the message 'the subscriber you have dialled is only prepared to receive calls from those who first identify themselves'. If network operators do not provide this facility, an innovative manufacturer can develop a telephone that will. The additional cost should be minimal.

Yours faithfully,

TIM SOANE

London, SW6

21 December