Liquid Level Indication with Madison’s Tape Level Indicator Requires No Electricity. Madison Company’s TL Series Tape Level Indicators are designed for simple and economical liquid level indication where no electrical power is available. Ideal for 30 or 55 gallon remote and mobile tanks, these devices incorporate a magnetic float and a standard tape measure blade that is sealed in a liquid-tight tube. Only the stem and float come in contact with the liquid, so the tape is always clean and easy-to-read. The retractable steel tape magnetically latches to the level position of the magnetic float.