for correction of the fault. This test is not limited to trouble isolation,
however; it is also used at the time of system installation just prior to
The intent of the test is not to condition the circuit, but
rather to see if impedance match falls within the stated requirements as
imposed by circuit parameters.
a. Test arrangement.
Typical circuit arrangements for terminal
impedance tests are shown in A and B of figure 1-12. Each wire in the pair
is shown separately.
The test will be made in each direction of
Each end station will record measurements on both the send
and receive sides of the circuit under test.
The test equipment includes
Telephone Test Set AN/USM-181 (IB 3321, figure 2) and a 600-ohm terminating
impedance data sheet (figure 1-13).
Analyzed data will be recorded on
Circuit Parameter Test Report, DD Form 1697 (to be shown in figure 3-3).
(1) Input circuit terminal impedance.
This test checks the impedance
at the input to the circuit under test.