It's a sad fact of life today that a great many homes are fitted with burglar alarms. Many of these alarms, especially low-cost self installed ones, don't have the facility to telephone the owner when an alarm occurs. If you were unfortunate enough to be away from home and have an unwanted visitor, you are dependent on someone making the effort to contact you, probably well past the time the incident occurred.

With this Alarm Dialler project connected to your alarm system, you will be notified within seconds of an alarm occurring, through a call to your telephone. And if you own a mobile telephone there's the added bonus that you can be virtually anywhere in the country and still receive the call. Once you are notified, you can then contact the authorities or a neighbour or friend for assistance.

As well as this obvious application, the project could also be used for other less critical uses; any time you want to be immediately informed that a particular event has happened.

The Alarm Dialler is an easy-to-build project using a PIC microcontroller and a handful of other inexpensive components, all housed in a small plastic box. The unit connects to a modem via a standard serial interface. It uses the modem to make and answer calls via your telephone line.

There are four alarm connection points on the rear panel, two for the alarm input and two that can be used to reset an external device. When in idle mode, it flashes a front panel LED and continually scans the alarm input connections.

If an alarm condition occurs, it sends commands to the modem to dial a preprogrammed telephone number. When you answer the call, you will hear a calling tone, and if the telephone has a calling identification display, you can also confirm that it is your alarm system calling.

The Alarm Dialler has many options, allowing it to be used in a broad range of applications. The various alarm input configurations are selected with a multi-way DIP switch, while other settings such as stored telephone numbers are programmed using a PC and a simple menu system.

Main Features PIC microcontroller based. Alarm input can monitor N/O or N/C contacts or an external voltage . Alarm reset output. No direct connection to the telephone line. Uses a stand-ard modem to make and answer calls. Dial in and test if system operational. Programmed easily via a PC. Programmable retry attempts; Primary and Secondary telephone number store. Alarm input inhibit switch. Automatic alarm reset option. EEPROM stores settings in case of power outage. Uses low-power 12V AC or DC power supply. Cheap and easy to build.