Single Line Communication in Fire Detectors

Hi All,

This is my first post here. I am basically a microcontroller programmer working with the Microchip range of products. I have been approached by a client to develop Addressable Circuits which could be retro-fitted in normal analog fire sensors.

I searched the internet to find information on how they communicate with the Fire Alarm Control Panel. I am looking for some pointers regarding the electrical circuitry, how both power and data are handled on the 2 wire loop, and the communication standards.

Thanks for looking.
Regards