An electrosurgical system comprising an engagement detection system ("EDS", 200) adapted to be positioned between, and in electrical communication with, an electrosurgical generator and an electrosurgical instrument , the EDS associated to a trocar cannula and adapted to electronically detect that the electrosurgical instrument is inserted into the trocar cannula , and thereafter deliver electrosurgical energy to the instrument; wherein the EDS further comprises: (a) a first connector for operably connecting the EDS to a surgical instrument; (b) a second connector for operably connecting the EDS to an electrosurgical generator; (c) a first switch mediating electrical communication between the first connector and the second connector; (d) a control circuit adapted to receive an electronic signal indicative of the electrosurgical instrument being inserted into a trocar cannula and generate a switch signal for controlling operation of said first switch; and the electrosurgical system further comprises a modular signal interface system ("MSIS", 210) for providing electrical communication between the EDS and an electrosurgical instrument when the electrosurgical instrument is inserted into a trocar cannula ; wherein said MSIS comprises: (e) a signal interface adapter provided on, or adapted to be mounted on a trocar , the signal interface adapter having a central aperture extending therethrough and a proximal face having a plurality of conductive contacts; and being further characterized in comprising (f) an instrument connector provided on, or adapted to be mounted on a shaft (2929 of a surgical instrument , the instrument connector having a central aperture extending therethrough and a distal face having a plurality of conductive contacts, the instrument connector adapted for providing electrical communication via a cable between one or more of said contacts and a surgical instrument on which the instrument connector is provided or mounted; wherein the signal interface adapter and the instrument connector are adapted for mating engagement such that, when matingly engaged, said central apertures are axially aligned and predetermined ones of the plurality of contacts of the signal interface adapter are in conductive contact with predetermined ones of the plurality of contacts of the instrument connector. (a) a first connector for operably connecting the EDS to a surgical instrument; (b) a second connector for operably connecting the EDS to an electrosurgical generator; (c) a first switch mediating electrical communication between the first connector and the second connector; (d) a control circuit adapted to receive an electronic signal indicative of the electrosurgical instrument being inserted into a trocar cannula and generate a switch signal for controlling operation of said first switch; and (e) a signal interface adapter provided on, or adapted to be mounted on a trocar , the signal interface adapter having a central aperture extending therethrough and a proximal face having a plurality of conductive contacts; and being further characterized in comprising (f) an instrument connector provided on, or adapted to be mounted on a shaft (2929 of a surgical instrument , the instrument connector having a central aperture extending therethrough and a distal face having a plurality of conductive contacts, the instrument connector adapted for providing electrical communication via a cable between one or more of said contacts and a surgical instrument on which the instrument connector is provided or mounted; <EOS>