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Watch Dog for Telephones

Watch Dog for Telephones

Most of the telephone security devices available in market are simple but quite expensive. A very simple and uni- que circuit of a telephone watch-dog to safeguard subscriber telephone lines against any fraud is described here. This little circuit keeps continuous watch over the telephone lines and sounds an alarm in case of any misuse.

http://www.electronicsforu.com/efylinux/circuit/cir67.htm

Home security project

Home security project

The security system application and program offers a simple demonstration of the BASIC Serial Interface. By adding only a few door and window switches, a transistor, a siren, (see schematic) and a few lines of BASIC program (see program listing) the interface can become a multi-function security system.

http://www.jbgizmo.com/page3.html

Home Security System

Home Security System

http://www.qsl.net/vu2upx/Projects/home_security.htm