Each ST317 fits inside the ST3000R or ST3000W housing.
The card has a mirror image of the inputs available on the ST300 Motherboard. Comes with 16 inputs (8 Digital & 8 Analog) programmable, and 8 Relay Dry Contact Digital outputs.
A maximum of 4 cards can be fitted to the motherboard for example: 4 expansion cards or if you use a ST330 Telephone card then you can only fit 3 expansion cards. Also any more than 2 extra cards require an expansion ribbon cable ST 450 Includes expansion cable.
Above: The Sentor ST317 I/O Expansion Module