Abstract: A tank level monitoring and alarm system comprises a passive level switch, a transmitter, a repeater, and a receiver. It provides easy installation, convenient calibration, and very low maintenance. A mechanical level switch for the specific vessel is installed. The contacts of the level switch are connected to the transmitter. When the switch is activated, the transmitter immediately broadcasts an alarm signal to the receiver. A relay output at the receiver is either opened or closed thus activating the alarm or other device attached to it. The relay output may also connect to a control apparatus, such as a signal transmitter to provide for remote operation of such devices as valves.