What is the HAT bus
From Safe Intercom - Technical Support
The H-series devices have a modular design that allows you to connect expansion modules with each other. The HAT bus is a specialized 1-wire protocol designed to enable two-way communication between all Safe H series devices connected to each other. Communication takes place with one wire, which is on the yellow cable on the 3-pin connector. Each slave device needs also power cables (GND and 12VDC). Everything is handled by easy installation on JST plugs.
