MSD Magnetic Pickup Tach Adapter # MSD8920MSD Magnetic Pickup Tach Adapter # MSD8920 Tach Adapter, Magnetic Pickup Ignition Systems, Each MSD magnetic pickup tach adapters maintain accurate tachometer readings. If you are using the magnetic pickup input (green and violet wires) to trigger your MSD Ignition, you will need one of these tach adapters. These units will correct the operation of most voltage triggered tachometers that do not work directly off of the tach output terminal of your MSD