Abstract: An electrosurgical instrument system for ready deployment of the instrument at the end of a line within a sterile surgical field employs a disposable reel detachably mounted on a base unit which allows smooth manual withdrawal and provides controlled motor-driven retraction of the line and instrument. The line includes power, control and ground circuits and the circuits are completed through a reel in a detachable cassette mounted on a base unit, which includes a tension-controlled belt permitting manual payout and controlled drive return of the line and instrument.