Abstract: A telephone conversion unit for substitution in a standard rotary dial telephone is disclosed wherein a keyboard coded telephone number is converted to a serial pulse train which simulates that generated by a standard telephone rotary dialer unit. The converter includes a keyboard switch having at least 10 keys for generating signals corresponding to each key depressed. An electrical encoder converts the signals into a four bit parallel signal with each encoded signal uniquely identifying a depressed one of the 10 keys of the keyboard. A dialer circuit means converts the encoded signal to a serial pulse train corresponding to the respective keys depressed. Power for the conversion unit is provided by converting the telephone line current coupled to the telephone unit when the hook switch is closed to a voltage suitable for powering the converter unit.