What is component 4 in figure T-2?

Erklärung
Component 4 is the transformer in the Figure T-2 power supply. An adjustable coil, a double-pole switch, and an adjustable resistive control have different symbols and do not identify component 4.

Component 4 is the transformer in the Figure T-2 power supply. An adjustable coil, a double-pole switch, and an adjustable resistive control have different symbols and do not identify component 4.