Electronics Diversified, Inc. (EDI) began manufacturing remote-controlled dimmer panels in 1967 and gained recognition for its rugged, portable touring “SCRimmer” dimmers. In 1982, EDI introduced the Mark VII — a high-density dimmer rack that competed directly with Strand’s CD80 and similar systems from Kliegl (K96) and Electro-Controls (EC-Quad).
If you’re working with aging EDI infrastructure, explore our upgrade solutions for EDI dimmer racks to keep these legacy systems running reliably in modern applications. And if you’re seeing inconsistent behavior in your system, don’t miss our guide to common dimmer rack failures for signs to watch for.
EDI Mark VII Dimmer Rack
Similar in size to the Strand CD80, the EDI Mark VII featured a single “Multi-Link” processor housed in the bottom of the rack. These racks supported a mix of:
- Dual 20-amp modules
- Single 60-amp modules
- Quad 20-amp modules
The quad modules increased total circuit capacity to 144 circuits per rack, compared to 96 in the CD80. Circuits are arranged top-left to bottom-right, left to right per row. Slot labeling was done at the factory to match specific module types.
Cooling System:
Two fans located behind the processor pull air through the modules and exhaust heat from the rack.
For owners experiencing flickering lights or non-responsive circuits, it may be worth reviewing the signs of processor or module issues in aging dimmer racks to identify early-stage failure points.
Architectural Control
Mark VII was among the first dimmer racks to support architectural (houselight) control. Originally, a pin matrix above the processor allowed assignment of dimmers to 0–10V DC channels. In 1994, EDI introduced TSC (Twilite System Control), which often mounted above the Multi-Link processor and featured a 3.5” floppy disk drive.
Visual Characteristics:
- Always painted black
- Black or silver dimmer modules
- Very few indicator lights on the Multi-Link processor
- No panic function to turn all circuits on manually
Despite these limitations, many 30–40-year-old Mark VII racks are still in service. With the right upgrades, these racks can be a cost-effective part of a 21st-century lighting system. Visit our EDI Upgrades page to learn more about retrofit processors, fan replacements, and module conversions.
EDI MX Dimmer Rack
Introduced in 1998, the EDI MX dimmer rack evolved the Mark VII design to better compete with ETC’s Sensor series. It is easily recognized by its blue paint and silkscreened “MX” logo on the front door. The dimmer modules, Multi-Link II processor, and TSC XLT architectural controller (if present) are painted white.
Mechanical & Layout Differences
Unlike the Mark VII’s horizontal module layout, the MX uses vertically stacked dimmer modules, with processing and architectural controls at the top. The left-hand side features:
- LED status beacons
- LCD display screen
- RJ11 port for portable programmer configuration
(And yes — Parlights still has a few of these programmers in the shop. We guard them with our lives.)
🧠 Fun Fact: The MX is the only vertical rack where circuit numbers run sequentially from top to bottom. Other racks like the ETC Sensor or Colortran iSeries jump circuit numbers across the cabinet — a major pain when you’re trying to find breaker 71.
Cooling System
Fans are located in the top of the rack, pulling heat upward through the modules. A Service switch on the right side of the Multi-Link II processor allows technicians to bring all channels to full.
Some MX racks may be branded Cooper Controls or Zero 88, following Cooper Lighting’s acquisition of EDI (and subsequent retirement of the product line).
Like the Mark VII, MX racks are still widely used and can deliver years of reliable service with proper upgrades and maintenance. If you’re unsure whether to repair, replace, or retrofit, see our guide to EDI dimmer rack upgrades for your best path forward.
Need Help with Your EDI System?
Parlights offers service, repair, and upgrade support for both Mark VII and MX dimmer racks — as well as a wide range of other legacy systems.
📞 Call us: 301.698.9242
📧 Email: service@parlights.com