摘要 |
<p>An alarm device is arranged to transmit an alarm signal indicative of an alarm condition being met. The alarm device accesses a record of a list of cellular networks available for communication with the device. The record includes information identifying each of the networks, and a measure of the reliability of communication over each network. The alarm device selects a network with which to establish a communication link based on the measure of the reliability of communication over the network, and attempts to establish a communications link with the selected network. The device is also arranged to make no more than a predetermined repeat attempts to connect with the selected network if previous attempts to connect fail. Subsequently, another network is selected to connect to based on the measure of reliability of communication over the network, and the device attempts to establish a communication link with that other network. The measure of reliability of communication over each network may be based on signal strength, such as the cell signal quality; signal to noise ratio; number of cells within effective range of the device; and bit error rate.</p> |