There are 4 screw terminals on the board:

• IN - the audio signal input from the secondary of the transformer
• COM - the common connection point between the two transformers - a "Ground" reference for the high Voltage bias
• HV - the High Voltage output
• ACC - an accessory connection which goes nowhere. I use it for the other secondary.

The wiring diagram for connecting this into your ESL is:

Please note that I don't include the primary wiring on this diagram. There are many sources for this, including HERE.

Here is a photo of a prior version of this board installed in the electrical panel of my Full Range ESLs:

If you are interested in purchasing these boards, either the bare board or a completed unit, send me an email. The bare boards are $10 each with completed and tested boards at $45 each. The completed boards are built to your voltage specifications.