This article introduces a PC-based radio-linked caller identification system. It consists of a central receiver and up to 16 caller units. The receiver is connected to a computer via the Centronics port. Each unit has a push-tomake button on it. When the button is pressed, the caller unit sends out a unique code to the soundings. The receiver intercepts the code and the computer decodes it and displays the number of the activated caller unit on the screen. The operation distance is about 75 metres in buildings and 200 metres in open fields.The system has a wide range of applications. In hotels, restaurant and shops, the caller unit can serve as a ‘Call Assistance’ button used by customers to call for assistance. It also has applications in interactive teaching environment in schools and colleges.The system utilises ‘2nd generation’ versions of FM radio transmitter and receiver modules (TX2/RX2) from Radiometrix Limited. The transmitter is a low-power device (LPD) type-approved to the Radiocommunications Authority (RA) specification MPT 1340 in the UK and Europe. This avoids the need to submit the project for final approval.