Along with the repeater units, most stations utilize duplexers. These are notch filters usually in an array of six, eight, and sometimes four units. They separate the transmitter and receiver signals from each other so one antenna and coaxial line can be utilized. While this solution is very efficient and easy to install, factors such as humidity and temperature can affect the performance of duplexers, so in most configurations a dryer is installed to keep humidity out of the duplexers and coaxial cable, along with heated buildings in which they are installed in. Excellent quality coaxial cable, connectors, and antennas must also be used, as a single-antenna is not as forgiving as a dual antenna system since any RF leakage or poor connection can greatly decay the reliability and performance of the repeater. In some applications, cables going from the repeater and duplexers must be tuned to mitigate these issues.