A wired intruder alarm and a wireless one work on the same basic principles as described above. The main difference is that with a wired system the signals are transmitted through cables, while with a wireless solution, the signals are transmitted through secure radio frequencies. In a completely wireless system, the main panel will be the only part of the alarm which needs cables in order to give electrical power to the system. All other accessories work on the wireless radio frequency principle and are powered through batteries. Batteries will need to be replaced (average lifetime is 2 years but varies upon usage) and one will be alerted as to which component needs a battery replacement via a message on the keypad.