A family of integrated logic circuits that was the first to be developed but is now little used. The input is through a resistor into the base of an inverting transistor. The basic NOR gate is shown overleaf. The output is high (corresponding to a logical 1) only if both the inputs are low (corresponding to a logical 0). If either input is high the transistor conducts and saturates and the voltage at the output is low. RTL circuits tend to be slow low fan-out circuits that are susceptible to noise but the power dissipated is low compared to emitter-coupled, diode-transistor, and transistor-transistor logic circuits.