Abstract: Initializing apparatus for use with circuitry mounted on a plug-in printed circuit board is described. Illustratively a telephone make-busy circuit is disclosed, which circuit automatically operates a make-busy relay on a plug-in telephone circuit when that circuit is plugged into a connector. A special "half" contact on the printed circuit board is connected to the control lead for the relay and when the circuit board is inserted into the connector, ground is momentarily applied to the contact and the relay control lead by a contact finger in the connector. The momentary ground causes the make-busy relay to operate for making the circuit appear busy to the telephone switching system. When the circuit board is fully inserted into the connector, the connector contact finger moves off the special contact on the circuit board and thereby removes the temporary ground.