Glossary:CT
A centre tap (CT) is a connection made at the mid point of a transformer winding. The two halves can then produce or be fed by two AC voltages equal in magnitude but opposite in phase. In a power supply this allows full wave rectification with 2 diodes instead of 4. In a Class B amplifier the two halves may be driven in opposite phase by two power transistors. In a balun the centre tap allows for the creation of equal and opposite phases, giving a degree of immunity to interference in a long cable.