| 摘要 |
A security module (2) has a motion detector (4), a microcontroller (6), antenna (8) and a radio tracking beacon transmission means able to transmit at a number of power levels or a number of duty cycles. The motion detector 4 detects motion of the security module relative to a cellular telephone network and detected motion triggers the radio beacon. The security module 2 may be adapted to be installed into the cash cassette of an ATM (Automatic Telling Machine) or any container in which valuable goods are stored. The radio beacon sends an alarm signal to a tracking module 10 using a slow duty cycle setting and once an acknowledgement is received from the tracking module, the radio beacon uses a faster duty cycle setting. In addition the alarm signal transmission event may comprise a number signals sent at different transmission powers, so that the lowest power that receives an acknowledgement may be used. (Fig 3 shows power level switching). |
