Abstract: By opening switches coupling a subscriber loop to circuits in a SLIC when an overvoltage condition occurs, the SLIC is protected from damage. The overvoltage is detected by a overvoltage protector behind the switches. The overvoltage condition is latched and the common control is notified of the condition. The common control may then clear the latch, reclosing the switches. If the overvoltage still exists, the switches are re-opened and maintenance personnel is notified of the fault.

Abstract: Disclosed herein is a Hall-effect liquid level sensing apparatus and method. The device may be mounted on a liquid storage tank and includes at least one float suspended within the tank and floating upon a hollow tube for guidance. The float carries a permanent magnet and a Hall-effect sensor may be reciprocated within the hollow tube to sense the location of the permanent magnet and thereby the location of the float. The device further includes a control device including an optical encoder which enables the device to sense the depth in the hollow tube to which the Hall-effect device has travelled when it senses the height of the permanent magnet. The invention may be used in conjunction with a plurality of floats to determine not only the liquid level but also the level between the liquid and a diverse liquid contained within the same container.