The purpose of this standard is threefold:1) 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.; 2) 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.; 3) 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. Balance circuits are used at frequencies extending well into the megahertz range and there may be a need for measuring longitudinal balance at high frequencies. The definition of degree of longitudinal balance and the general configuration of the driving test circuit given in this standard are applicable at all frequencies. However, the test circuit impedances and other requirements for measurement outside the voice band are beyond the scope of this standard.