The Model 409 is a compact, socket-mount device for level control of conductive liquids. The internal relay is energized when operating power is applied. When the liquid level reaches the probe, the relay de-energizes. When the level drops below the probe, the relay will reset. A fixed, two-second time delay prevents oscillation due to wave action. Probe cables may be shielded or unshielded. If the liquid container is made of a non-conductive material, a common electrode is required. Other features include an LED indicator to show the output relay status and an adjustable sensitivity setting.