CABLES are uses to connect SENSORS to the Transmitter Control Unit (TCU), There are two jacks at the rear of the TCU to plug in CABLES from SENSORS. The CABLES are very similar to the wires connecting a phoneset to a wall jack (the actual dimension of the jack is slightly smaller, however.) CABLES are available in ten and twenty foot lengths. If the distance between where you want to locate the SENSOR and the TCU is longer, get additional lengths and COUPLERS to join the additional lengths (one COUPLER for each join).