Telephone receiver call device - has magnetic cassette with tape to give pleasant and continuous sound or recorded music

摘要

A call bell or buzzer of a telephone receiver may be replaced by another call device with a harmonious and continuous sound. The call device has a magnetic tape cassette. The cassette has pre-recorded music or other sounds according to choice and the device uses the voltage supply to the bell to switch on the cassette. The call signal is injected acted into a transformer and the output of the transformer is connected to a rectifier. The signal is then filtered by a capacitor to obtain DC at 15 volts. This voltage excites a relay which can switch-on the supply to the cassette. The value of the capacitor is chosen to maintain continuous excitation of the relay. A push-button is used to discharge the capacitor and to reset and relay when the receiver is lifted off the telephone.