Manual call points are used to initiate an alarm signal, and operate by means of a simple button press or when glass is broken revealing a button. They can form part of a manual alarm system or an automatic alarm system. There will be an indicator on the monitoring unit for visual indication to locate the call point easily, and there should be a visual identifier of the unit which triggered the alarm, typically a mechanical flag which operates on a latch and must be manually reset, e.g. by a key.