...The technical information contained in this ZIP file should provide enough information to assist an experienced computer science hobbyist, student, or teacher in building a fully functional two-station, wired alarm system that involves two companion circuit boards that communicate with each other through a three-wire serial (full duplex) communication link. There are improvements, modifications, and enhancements that can be made to this information. Included are hardware schematics, Fritzing PCB CAD layout files plus etchable PDF's, wiring diagrams, part numbers of components, pictures of working units, commented software source code listings as well as precompiled HEX file for programming the PIC16F690 microcontroller that is on each of the two circuit boards. The circuit board layouts are single-sided to enable a hobbyist to etch her/his own boards. ...