I am trying to troubleshoot a dual-energy heating installation. I found this diagram from the electrical company. The terminals below the meter face are labeled O, N, F, 12, and VCA. 12 I think is 12 volts, VCA is alternating current. These are in French so I'm guessing O, N and F are as well. If it helps: two of these terminals should act like a thermostat and close the circuit at a certain temperature (not sure which two,that's what I'm trying to troubleshoot). I'm not sure what the third one does.