External Power Supply Unit he S-240P is designed to be used with the M-5000, S-4000S or S-4000H units that are part of an S-4000 Modular Digital Snake. The S-240P supplies power to, and allows the continued operation of, the M-5000 or S-4000 unit that it is connected to in the case the internal power supply of the M-5000 or S-4000S/H is damaged and fails; or if the power switch on the unit is accidentally turned off. In these rare and unexpected cases, the S-240P will allow the S-4000 unit to keep working and the audio of the system will continue without interruption. For this reason, it is suggested that, whenever possible, the S-240P should be plugged into a circuit that is separate from the circuit supplying the power to the M-5000 or S-4000S/H.