The HEF4066B has four independent bilateral analogue switches (transmission gates). Each switch has two input/output terminals (Y/Z) and an active HIGH enable input (E). When E is connected to VDD a low impedance bidirectional path between Y and Z is established (ON condition). When E is connected to VSS the switch is disabled and a high impedance between Y and Z is established (OFF condition). The HEF4066B is pin compatible with the HEF4016B but exhibits a much lower ON resistance. In addition the ON resistance is relatively constant over the full input signal range.