An HVAC system, comprising: a thermostat unit comprising an interface operable to permit a user to issue commands to the HVAC system; an equipment interface module, EIM, communicatively coupled to the thermostat unit, configured to: receive a command from the thermostat unit; identify a component of the HVAC system based on the command; select an electrical wire from among a plurality of electrical wires based on the identified component of the HVAC system; generate a reference AC signal; identify a time period based on the command, wherein the time period corresponds with operating instructions for the identified component of the HVAC system; periodically remove half-cycles from the reference AC signal at each time period to generate an encoded AC signal; and transmit the encoded AC signal to a control unit using the selected electrical wire, wherein: transmitting the encoded AC signal comprises superimposing the encoded AC signal onto an AC power signal; and the encoded AC signal has a higher frequency than the AC power signal; and the control unit coupled to the EIM via the plurality of electrical wires, configured to: receive the encoded AC signal; identify the component of the HVAC system based on the electrical wire where the encoded AC signal was received; decode the encoded AC signal to obtain the operating instructions, wherein decoding the encoded AC signal comprises determining the time period corresponding with the operating instructions based on the frequency of removed half-cycles from the reference AC signal; and control one or more functions of the identified component of the HVAC system according to the decoded operating instructions. a thermostat unit comprising an interface operable to permit a user to issue commands to the HVAC system; an equipment interface module, EIM, communicatively coupled to the thermostat unit, configured to: receive a command from the thermostat unit; identify a component of the HVAC system based on the command; select an electrical wire from among a plurality of electrical wires based on the identified component of the HVAC system; generate a reference AC signal; identify a time period based on the command, wherein the time period corresponds with operating instructions for the identified component of the HVAC system; periodically remove half-cycles from the reference AC signal at each time period to generate an encoded AC signal; and transmit the encoded AC signal to a control unit using the selected electrical wire, wherein: transmitting the encoded AC signal comprises superimposing the encoded AC signal onto an AC power signal; and the encoded AC signal has a higher frequency than the AC power signal; and receive a command from the thermostat unit; identify a component of the HVAC system based on the command; select an electrical wire from among a plurality of electrical wires based on the identified component of the HVAC system; generate a reference AC signal; identify a time period based on the command, wherein the time period corresponds with operating instructions for the identified component of the HVAC system; periodically remove half-cycles from the reference AC signal at each time period to generate an encoded AC signal; and transmit the encoded AC signal to a control unit using the selected electrical wire, wherein: transmitting the encoded AC signal comprises superimposing the encoded AC signal onto an AC power signal; and the encoded AC signal has a higher frequency than the AC power signal; and the control unit coupled to the EIM via the plurality of electrical wires, configured to: receive the encoded AC signal; identify the component of the HVAC system based on the electrical wire where the encoded AC signal was received; decode the encoded AC signal to obtain the operating instructions, wherein decoding the encoded AC signal comprises determining the time period corresponding with the operating instructions based on the frequency of removed half-cycles from the reference AC signal; and control one or more functions of the identified component of the HVAC system according to the decoded operating instructions. receive the encoded AC signal; identify the component of the HVAC system based on the electrical wire where the encoded AC signal was received; decode the encoded AC signal to obtain the operating instructions, wherein decoding the encoded AC signal comprises determining the time period corresponding with the operating instructions based on the frequency of removed half-cycles from the reference AC signal; and control one or more functions of the identified component of the HVAC system according to the decoded operating instructions.