Unison DR Dimming Racks originally did not have a neutral connection. Sensor racks have always had the Neutral connection. For this reason, D20F dimmer modules with a Q142 power cube would work in a Sensor rack, but not in a Unison rack. In original DR racks, the D20F power cube was changed to a Q141.
If you have a Sensor Rack or a Unison Rack with the neutral on the signal distribution card, your D20F's will work better with Q142's. If it is an older Unison rack without the neutral on the signal distribution PCB, your D20F's will work better with Q141's.