A modular surgical instrument system, comprising a handle assembly, comprising a disposable outer housing configured to define a sterile barrier. The disposable outer housing comprises a first housing-portion and a second housing-portion movable relative to the first housing-portion between an open configuration and a closed configuration. The handle assembly further comprises a control inner core receivable inside the disposable outer housing in the open configuration. The disposable outer housing is configured to isolate the control inner core in the closed configuration. The modular surgical instrument system further comprises a primary wired interface configured to transmit data and power between the control inner core and at least one of modular components of the modular surgical instrument system, a secondary interface comprising a sensor located within the outer housing, and a control circuit configured to confirm a primary connection through the primary wired interface based on at least one sensor reading.