Abstract: In an extension (or second) telephone set, a logic circuit powered by standard line current is connected between the standard telephone key encoder that receives and encodes the user entered key dialing digits and a dialing signal converter that produces dialing pulses on the phone line in response to the encoder. The converter accepts binary encoded digits from the encoder along with a strobe signal associated with each entered binary encoded dialing digit. Logic gates assisted by other digital circuitry determine whether the initial digit of the series is authorized and, of so, allow the associated strobe signal to be transmitted from the encoder to the outpulsing converter and thereafter allow a predetermined maximum number of digits of the series to be communicated to the converter to complete the local outbound call dialing.