The RD-2033 module controls the power regulation for the rack.
The RD-2031B Module is your signal converter card. This card converts your incoming console control signal (either DMX or LMI protocol) into a control protocol called Micro2 which is used by the RD-2034 modules to turn the lights on and off. This card is not used in all systems, only systems with a DMX or LMI control console. If you were to remove this module you would see a chip with a sticker containing your system number on it. All of these cards contain site specific custom programming.
The RD-2034A Modules are your dimmer firing cards. These convert the Micro2 signal from the 2031B card into Pulse width signal to fire the dimmers and dim your system. These modules are addressable based on your system configuration and each card controls a phase of dimmers in the rack. As you can tell by looking at the rack there are 6 2.4k modules across each row. Phasing is based on each module slot. For the dimmers this phasing is A,B,C,A,B,C in each row. The addresses on the front card determine the signal start number and the rest of the electronics are smart enough to understand which dimmers get fired based on what the console is turning on. In most systems the cards are addressed as 1,5 and 9.
So looking at the top row
The Left hand 2034 card controls 1,2,7,8
The Center 2034 card controls 3,4,9,10
The Right hand 2034 controls 5,6,11,12
This continues through the rack in series. Based on this if you are having a problem with one of these cards the associated dimmers to the card will be affected.
The RD-2035 cards are analog control cards which control Houselights/Architectural lights. These cards combined with a series of relays wired to the back of the rack behind the cards and interpret button hits from your house and panic control stations and their faders. The button hits on the stations trigger the relays inside the rack and the faders send analog control signal to the card which converts the analog signal into pulse width signal to turn the dimmers on and off. In most systems the houselights are not controlled by the console and the console cannot control the houselights. In all cases the stations are hardwired to the relays and it was custom installed. If you need to troubleshoot the architectural side of the system job prints are essential.