A safety system and a method using a safety system having at least one mobile key unit (2) with an evaluation unit (3) and having a key station (4) with a receiver for the key unit (2), wherein at least one spatially restricted access zone (6) is arranged having an access station (7) for a facility (8), wherein the key unit (2) is configured for reading data from at least one checking station (9) within a safety zone (16) of the facility (8), wherein the data comprise identification data for the checking station (9), and wherein the mobile key unit (2) has an interface (10) by means of which the data can be wirelessly transmitted from the checking station (9) to the key unit (2), with the checking unit (9) only being accessible via the access zone (6) so that the access zone (6) can be passed through by a person (17) having the key unit (2) before reaching the checking station (9) and after the leaving of the checking station (9), with the data of the key unit (2) being able to be transmitted to the key station (4) when all the mobile key units (2) are in the key station (4), and with the facility (8) being deactivated or blocked when at least one key unit (2) has been removed from the key station (4).

A method for operating an access control comprises creating a plurality of wake-up schedules for a wireless transceiver. Each of the plurality of wake-up schedules may be configured to control how frequently the wireless transceiver wakes up to transmit or receive information. Each of the plurality of wake-up schedules for the wireless transceiver may be different from another one or the plurality of wake-up schedules for the wireless transceiver. The method may further comprise automatically switching between the plurality of wake-up schedules for the wireless transceiver such that a duration of time between wake-ups for the wireless transceiver radio is shorter during some predefined times and longer during other predefined times. The duration of time between wake-ups for the wireless transceiver may be configurable by an administrative user via an interface.

An access-control system comprises using an access management server, a lock, and multiple instances of time-based codes. A time-based code may be input to a lock by physical presses on a keypad; radio communication (Bluetooth, RFID, NFC, WiFi); a sound or audio signal; touch or vibration pattern; light pattern of intensity or contrast); and/or a sequence/pattern of temperature changes.