Power supplies for the controller are generated from the single phase auxiliary supply via a Switched Mode Power Supply. The incoming supply is
directly rectified to provide a high voltage dc power rail. A high voltage transistor switches this rail onto the primary of a high frequency transformer,
the output of which is rectified and smoothed to provide the dc power supply rails. The 5V dc rail is monitored via a reference element and a control
signal returned via an opto-isolator to the control element of the high voltage switching transistor. The other dc rails (-15V & +24V dc) are generated
via separate secondary windings which are rectified and smoothed, with individual linear regulators providing ±15V dc rail. The SMPS operates over
an input voltage range of 115V to 230V ac ±10%, 50/60Hz.