Q: Why does my display show “ZZ”?

A: This normally means that the MICRO COMM® driver is either getting no floor signals or the signals are the wrong voltage and/or polarity.

1. If you have an SMCDU-XXX driver, the value of the R1 – R10 resistors will determine the signal voltage it is expecting. For 6 to 20 VAC/DC the value will be 820Ω (grey, red, brown, gold); for 24VAC/DC the value will be 6.8KΩ (blue, grey, red, gold); for 120VAC the value will be 18KΩ (brown, grey, orange, gold); and for 125VDC the value will be 39KΩ (orange, white, orange, gold).  If you are not using a binary decoder with the SMCDU it will work with positive or negative DC signals, just make certain that the GRN/BLK and/or the GRN/WHT wires have been connected to the correct return for the floor signals.
2. If you have an MCCA-XXXXXXX driver, the value of the R1 – R13 resistors will determine the signal voltage it is expecting.  The values and color codes are the same as the SMCDU.  If the signal voltage is AC, then the MCCA will not care about polarity, but if the signal voltage is DC, then it must match the way the board was built.  The second character in the part number (MCCA-4XXXXXX) will tell you what voltage and DC polarity it was set up for.
   1. A = +6 to 20 VAC/DC
   2. B = +24 to 48 VAC/DC
   3. C = 120VAC (will always expect a +DC voltage)
   4. D = +125 VDC
   5. E = -6 to 20 VAC/DC
   6. F = -24 to 48 VAC/DC
   7. G = -125 VDC

If your signal voltage is DC and you have the wrong polarity board, you will need to contact someone in our sales department and order a new board that is set up for the correct polarity.