Testing Patches

TM11-5895-932-14&P

diagram prior to performing patching for testing.

b. Isolator Substitution (fig. 3-2). Isolator

The types of tests, the performance standards and

substitution involves the multicircuit (12-wire)

procedures to be used for these tests are contained

patch cords. In this case, it is assumed that

in various DCA manuals, listed in appendix A.

operational spares for the isolators are connected

to circuit 19. On the black patch, the MODEM

3-7. Patching for Fault Location

jack of circuit 2 is connected to the COMP jack of

Patching for fault location includes loopback by

circuit 19. On the other side of the isolator cabinet

use of special test cords and plugs and use of the

(red dc unsecure patch), the MODEM jack of

BERT for troubleshooting.

circuit 19 is connected to the COMP jack of circuit

a. Loopback Loopback is a method for con-

number 2 to complete the patch.

necting the transmitting lines of a communication

3-6. Testing Patches

device to its received lines. The purpose of the

loopback is so that a standard, or test message

Testing patches, as described here, are defined as

those patches which connect the analog test

may be sent from and to the communication device

equipment (noise measuring set, transmission

for comparison of the transmitted to the received

measuring set) into the vf lines. The patching

message for testing purposes. At the PTF, request

arrangements for these patches are shown on

for loopback comes from either the AMME or the

figure 3-3. A schematic a n d a d r a w i n g

remote terminals. Two special loopback cables and

representing the way the actual patch cords are set

one special plug are provided at the PTF. The use

up are shown. PTF personnel should study this

of the cables and plug is illustrated in figure 3 -4.

3-4