The AZS fail-safe delay timer serves for the secure measurement of a preset time. The enabling signal for the control system, which for example makes it possible to open a guard device, is only given when the present time has elapsed. AZS range fail-safe delay timers are often used where dangerous situation can occur after a machine or plant has been switched off, e.g. because of running-down movements. Depending on the external circuit arrangements, the protection system can be secured up to the requirements of Control Category 3 to EN ISO 13849-1 in combination with an AES or AZR range safety monitoring module.