ANSI/IEEE 455-1976

This standard is based on a resistive test circuit, although pure resistance is not essential. Resistive elements are specified because they are generally considered easy to duplicate and balance. Repeatable and consistent balance numbers are the object of issuing this standard

The first purpose of this standard is to define the basic requirements of a test circuit which can be used to measure longitudinal balance. This test circuit will be capable of yielding consistent and repeatable test results. The second purpose is to define test conditions to be established while using the test circuit. Standard test conditions are considered vital for obtaining consistent results from a suitable circuit. A third purpose is to describe standard test procedures to be followed when the test circuit is operated. This standard specifies the elements of the test circuit only in general terms to allow considerable freedom when a test set is being designed. It thereby precludes the possibility that only one set of circuit elements will be capable of meeting the standard. This standard is based on a resistive test circuit, although pure resistance is not essential. Resistive elements are specified because they are generally considered easy to duplicate and balance. Repeatable and consistent balance numbers are the object of issuing this standard.

New IEEE Standard - Superseded. Telephone companies and equipment manufacturers have generally agreed on a definition for longitudinal balance for many years. This agreement extends also to the basic approach followed when measuring balance. Testing a device for balance involves the application of a longitudinal voltage. Then any resulting metallic voltage is measured, and the ratio of the two voltages is used to develop a balance number. Unfortunately, agreement has ended at about this point. A number of different test circuits are used by different segments of the telephone industry. Although all of the existing test circuits have some merits supporting their use, the mere existence of varied circuits leads to differences in test results. In addition to differences related to the test set, test conditions and procedures can also affect the result. When an item of equipment is to be tested, there is often a test set or procedure,or both, capable of giving any desired result. Agreement on one way of testing for longitudinal balance has been sought. This standard represents such agreement. It defines the basic requirements of a standard test circuit. Reasonable tolerances are included so that a test-set designer will find considerable latitude to make the set his own way. Besides defining the requirements for a test circuit, this standard includes test conditions and procedures that must be established and followed. As a result, all test sets designed and used in accordance with the standard will produce the same balance number for a given test specimen. Similarly, comparing balance numbers for different devices will become more meaningful when all come from tests meeting the standard.