A control system for technical installations , comprising a safety circuit , at least one stationary control device with input and output interfaces for establishing line connections to a technical installation to be controlled, at least one electronic hand-held terminal portable and usable in a mobile manner by an operator for influencing and observing control processes and states of the control system , and/or a technical installation connectible thereto, which hand-held terminal has a wireless control communication interface and also a control technology communication interface which can be established via a connecting cable , wherein each of which communication interfaces make a data integration of the hand-held terminal into the control system possible, at least one safety switching element on the hand-held terminal that can be actuated by an operator , which safety switching element is provided at least for a termination of potentially safety-critical control commands or motion sequences, a safety circuit , which is closed in the normal state, which safety circuit is transferable into an interrupted or open state for averting a hazardous state and is provided for termination of potentially dangerous motions or processes of a controlled technical installation or for causing a safe state in a controlled technical installation , and wherein the wired, control communication interface comprises a contact-based plug-in interface on the hand-held terminal , which plug-in interface has a first coupling element on the hand-held terminal and a second coupling element which can be coupled or decoupled as needed with respect to the first coupling element , which second coupling element is formed on the connecting cable , characterized in that at least one termination indicator is formed immediately in the second coupling element or in immediate proximity to the second coupling element on or in the connecting cable , which termination indicator is electronically detectable by a termination indicator detection means , that a hand-held terminal detection means is formed, which is provided for detecting the presence or non-presence of a control connection of a hand-held terminal to the control system , and that the control system , upon detection of a change from a presence to a non-presence of a control connection of the hand-held terminal and upon simultaneous detection of a termination indicator on the corresponding connecting cable to this decoupled hand-held terminal , recognizes a separation of the contact-based plug-in interface intentionally carried out by an operator on this hand-held terminal , and consequently, as a substitute for the subsequently ineffective safety switching element on the decoupled hand-held terminal , couples the last valid switching state of the safety switching element into the safety circuit in a functionally equivalent manner, and/or is designed for bridging the safety circuit as part of the unplugging of the hand-held terminal , or is provided for switching over from at least one substitute and/or parallel contact to the safety switching element on the hand-held terminal , provided that the safety switching element on the decoupled hand-held terminal was present in its non-actuated state or non-operating state immediately before the unplugging of the connecting cable from the hand-held terminal . <EOS>