Wireless Alarm

Iv been thinking about building a wireless alarm for my HNC Electronics project. Im hoping to use a 433 mHz transmitter in the centre of an office. This will then transmit to a reciever circuit in various pieces of office equipment. If the reciever is taken out of range of the transmitter an alarm will sound.

Does anyone know of any websites or books i can read to assist me in building this project? Any help is appreciated as i have very little experience with transmitters/recievers!

Thanks, Gav

https://img.photobucket.com/albums/v320/cymru09/first_draft-2.jpg

Here's a first draft of my circuit. Please could someone have a quick look over it for me?

The top circuit is one of four transmitters. For transmitter one, switch one would be closed. For transmitter two, switch two would be open, etc. This would then transmit to the reciever (lower circuit). If a transmitter goes out of range the relevent LED should light up and the buzzer would sound.

Could i transmit to only one reciever using the four transmitters at the same time?

Ask if you need any more info

Thanks

Having two or more devices transmitting simultaneously on the same frequency, the resulting signal will be a real mess. The idea will not work.

One possible way would be to have transmitter#1 transmit for 5 and then turn off, transmitter#2 on/off, transmitter#3... you get the idea?
The problem here would be synchronising the transmitters so that they dont transmit at the same time.

JimB