This card is the ‘distribution point’ for all other I/O Cards. It has a DB-25 connector to connect to the USB Expension Card and a DB-9 connector to connect to the Relays Card. Furthermore there are four flatcable connectors.
One of these connectors is for daisy chaining up to a maximum of four Display Cards (each for a maximum of 16 7-segments displays) and/or Outputs Cards (each for a maximum of 32 leds with the possibility of dimming them). Since an Outputs Card has double the amount of connections as opposed to a Display Card, you need to take in considration that the Outputs Bus can control a maximum of 64 outputs. So if you are planning to use one Outputs Card, a maximum of two Display Cards can be used in the daisy chain.
If four Display Cards are daisy chained a maximum of 64 7-segments can be controlled. If two Output Cards are connected a maximum of 64 leds can be controlled complete with dimming.
A second flat cable connector is for connecting an Output Connection Board. With this you can control a maximum of 38 outputs.
A third and fourth flat cable connector are for connecting Input Connection Cards. There are two types of these cards. One only with support for 36 inputs and one with 36 inputs and four encoders for which also hardware is present.
Furthermore a separate encoder card is available on which two encoder circuits are present both of which use two inputs from the Input Connection Board.
I use two Mastr cards to control my Overhead panel.