The two types of monitoring systems available are remote and local. Remote alarm systems are used to connect the control unit to a predetermined monitor. These systems come in many different configurations. High-end systems connect to a central station through a direct phone wire or fiber optic cable. The alarm monitoring also consists of motion sensors, and a communication wire.
More modern systems incorporate a digital telephone dialer unit that will dial a central station through a public switched telephone network and activate the alarm, either with a synthesized voice or increasingly through an encoded message string that the central station decodes. These may connect to the regular phone system on the system side of the demarcation point, but typically connect on the customer side ahead of all phones within the monitored premises so that the alarm system can seize the line by cutting off any active calls and notify the monitoring company when needed
Many alarm panels are equipped with a backup dialer capability for use when the primary PSTN circuit is not functioning. The redundant dialer may be connected to a second phone line, or internet interface device to bypass the PSTN entirely, to perhaps overcome intentional tampering with the phone lines. Just the fact that someone tampered with the line could trigger a supervisory alarm within the radio network, giving early warning of an imminent problem.
Wired systems also have the advantage, if wired properly, of being tamper evident. Wireless systems, on the other hand, often use battery powered transmitters which are easier to install. However, these transmitters may reduce the reliability of the system if the sensors are not supervised, or if the batteries are not maintained. Depending on distance and construction materials, one or more wireless repeaters may be required to get the signal reliably back to the alarm panel.
Hybrid systems utilize both wired and wireless sensors to achieve the benefits of each. Transmitters, or sensors can also be connected through the premises electrical circuits to transmit coded signals to the control unit. The control unit usually has a separate channel or zone for burglar and fire sensors. But there are better systems that have a separate zone for every unique sensor, as well as internal “trouble” indicators.