A control system for technical installations includes at least one electronic manual operator-control instrument that can be carried and used mobilely by an operator-control person for influencing and observation of the control system or a connected technical installation. The instrument has a wireless communication interface and a communication interface established via a connecting cable. At least one safety switching element actuated by the person on the manual operator-control instrument can at least terminate potentially hazardous control commands or movement sequences. The hard-wired communication interface includes a contact-based plug interface on the instrument having a first coupling element on the instrument and a second coupling element coupled and decoupled as needed relative to the first coupling element. At least one termination indicator on or in the connecting cable directly in or near the second coupling element can be sensed electronically by a termination-indicator detector.