Disposable Ground/Reference Electrodes (green). These are the single needle electrodes which are used as ground or reference connections to the preamplifier. 20mm Ground Electrode. Please Note: P/N 1705-00 is also used as the ground electrode when using a monopolar probe (P/N 3602-00 or 1574-00). When using it as a stimulator ground, it should be connected to the WHITE connector on the Stimulator Pod. The BLUE connector of the stimulating probe should be connected to the BLUE connector on the Stimulator Pod.