Abstract: A telecommunications line test system wherein a digital telecommunications network is electronically sectionalized via at least one master test unit in combination with at least one remotely addressable field loopback unit whereby the defective line section is isolated by progressively looping back test data as transmitted from a master test unit. Each field loopback unit, when properly addressed, will loopback to both the near side and the far side of the line so as to enable a given loopback unit to be reset (inactivated) from either side of the line.

Abstract: A system for measuring the level of a fluid in a tank comprises a plurality of reflectors positioned in the tank with the reflectors being a known distance from one another and a first reflector being an unknown distance from the top of the tank and an apparatus for producing and outputting a sonic signal and for receiving echoes from the plurality of reflectors and a surface of the fluid in the tank. The apparatus produces electrical signals representative of the received echoes. The apparatus includes a processor responsive to the electrical signals for, (i) calculating the distance between the apparatus and the first reflector, (ii) calculating the distance between a last reflector and the fluid surface, and (iii) determining the total distance from the apparatus to the fluid surface based on the distances calculated in (i), (ii), and the distance between the first and last reflectors.