D+40+0 Tangent galvanometer: Compass needle pivots in a coil.
D+40+2 Elementary galvanometer: Coil on spring in magnetic field.
D+40+4 Mavometer: Ammeter / voltmeter / galvanometer
D+40+6 Various meters for display.
D+40+8 Ammeter shunt: Only a small current flows to the meter.
