Abstract: A device for the monitoring of objects and/or persons is described which comprises an RF transmitter (10) and a security tag (15) with a casing for accommodating an electronic circuit. The electronic circuit contains a battery and an alarm circuit (30). An alarm is triggered when an electrically conductive security element (14) for attaching the security tag (15) to the object or to the person is severed or when an external RF field generated by the RF transmitter (10) has a defined state. The RF transmitter (10) is here designed with an encoder (11) for coding the RF signal, while in the electronic circuit of the security tag (15) a decoder (20) is provided which outputs an alarm signal to the alarm circuit (30) to trigger an alarm when a defined information content of the coded RF signal is present.