iam making now a home automatcion and i will make a laser on all doors in the home. then i want when the laser is cut it send to pc a plus as alarm..... and i found this circuit:
Schematic Of Transmitter **broken link removed**
Schematic Of Receiver **broken link removed**
now:
1- what is the change i must make it "like remove the speaker and t1"
2-can i use a laser pointer to generat laser?or anther device?
i didn't really understand question 1, but i did #2. You could definately use a laser pointer, it would use less pwr than the high pwr supply. Also, you could use infrared. this would use even less power. go to google.com and type in alarm schematics and you will get all kinds of laser, infrared, vibration sensor, etc, etc. alarm systems.