TM 11-6625-441-34
a. Power to energize relay K1 is obtained
2-4. Self-Test Circuit Functioning
through switch S7, fuse F1, and pins 37 and 20 of
test cable connector P1, through relay K1, pins 4
and 19 of connector P1, and to ground. When
The self-test circuits check the performance of the
relay K1 energizes, lamp 11 goes out, contacts D1
receiver and transmitter circuits and controls of
and D2 of relay K1 close, allowing current to flow
the interphone test set. The self-test check is
through lamp 12 to ground, lighting the lamp.
accomplished through the use of SELF TEST
Contacts B1 and B2, and C1 and C2 also close,
RECEPTACLE J8, relay K1, test cable con-
thus completing the self-test circuits.
nector P1, and the placement of toggle and
b. Proper operation of the interphone test set
selector switches to predetermined positions.
during the self-test check is verified by the
During self-test operation, the interphone test set
lighting and going out of lamp 13 when switches
is connected to a 28-volt dc power supply, and
S1 through S5 are placed in various position
test cable connector P1 is connected to SELF
TEST RECEPTACLE J8.
2-6
