Use of Troubleshooting Charts

TM11-5895-932-14&P

etc. Source of the information contained in the

b. Use of the BERT in testing a typical com-

munications system is shown in figure 4-1. In this

station drawings are as follows:

a. Cable runs-routing through cable ducts

case, the BERT is connected into the modem side of

b. Cable pair color coding connections

he black patch panel to supply signals to the

c. Cross connection diagrams

modem, the communications lines, and the remote

d Location, stenciling of terminal blocks

terminal modem. The lines are looped back at the

e. Schematic diagrams

mints shown separately, progressing from left to

(1) Fuse and alarm panels

right on the diagram At each loopback point, the

(2) Patch panels.

BERT is operated and the number of errors

(3) Major alarm panel

totalized. is noted. A significant increase in errors,

f. Connection and distribution of

caused by the addition of a loopback segment,

(1) DC power.

pinpoints the cause of the trouble to that added

(2) AC power.

segment. If the modems prove defective by this

(3) Intercom.

method, they should be replaced. If the com-

munications lines prove defective they should be

4-13. Use of Troubleshooting Charts

further tested, using conventional analog techniques

Troubleshooting of this facility is based upon

and then report this trouble, symptom, and

malfunctions that may occur during normal

measurement to the maintenance personnel

operation of the equipment in the system When a

responsible for the communications lines

trouble occurs, refer to the "Trouble Symptom"

4-12. Station Drawings

column in the chart Perform the checks and

corrective measures indicated in the "Check and

In addition to this manual, a considerable amount of

Corrective Maintenance" column to locate and clear

maintenance data which is used for troubleshooting,

the trouble.

is contained in the station drawings. Site personnel

must become familiar with the information contained

in them and in their use, numbering system, order,

4-14. Troubleshooting C hart

for

Major

Alarm

Panel.

Check and corrective

Trouble symptom

Probable trouble

maintenance

_ _ - --

--- __. - -

------

Check for trouble as indicated by

No audible tone from audible in-

a Tellite has been pressed, locking

switch line

dicator with a switch illuminated

out audible tone

Provide ground to audible in-

b Gnd from alarm panel not being

dicator with jumper wire If

extended to audible indicator

alarm does not sound check for

voltage at audible indicator If

voltage is present audible in-

dicator is defective

(1) If alarm sounds when ground

is provided, circuit trace ground

back to alarm panel

(1) If voltage is not found at

alarm, trace voltage back to -48

vdc power supply

c Gnd not being extended through

If no ground is found coming out

alarm panel

of alarm panel it will be

necessary to remove alarm panel

from rack to gain access to the

component parts With the top

and bottom covers removed. make

a continuity check from the pm

number corresponding t o t h e

illuminated lamp to switch pins

NC1

COM1

Refer

LBAD-D-33163, symbol SW3.

for switch location If continuity

is obtained on COM1 but not

NC1, this indicates a defective

switch Care must be taken to

insure that the (+) lead of the

VOM IS connected to the

corresponding lead (1-45) This

4-7