A portable apparatus for demonstrating the operation of one or more telephones by simulating an active telephone line in which a ring tone generator (74), busy tone generator (72), dial tone generator (70), confirmation tone generator (146) and power ringer (52) are operationally controlled by a microprocessor (62) responsive to the on-hook and off-hook status of a telephone connected to the apparatus as well as control signals established by keypad entry or programmed operation. A decoder (64) responsive to DTMF or pulse dial signals provides for universal operation without regard to the type of telephones connected to the apparatus. Communications over the telephones can be monitored with an external speaker (38) or headphones, or recorded for later review. The apparatus also provides for simulated operation of coin-operated and calling card operated telephones.