What’s the difference between the HSM2204 and the HSM2208?
The HSM2208 has 8 low current PGM outputs. These can be used for things like triggering relays or powering an LED indicator. The HSM2208 draws all of its auxiliary power from another device, usually the main control panel.
The HSM2204 on the other hand provides its own power, up to 1 amp, and requires its own power transformer and backup battery. It only has 4 PGM outputs and they can handle a higher current draw making them useful for things such as sirens. It can also be used to provide auxiliary power to other devices such as keypads or even an HSM2208.