Figure 3-1. Operator's controls and indicators.

TM 11-6625-922-15

Figure 3-1. Operator's controls and indicators.

b. End-to-End with Return Reference. When two

3-3. General Operating Procedures

transmission lines are available, one of the lines can be

used to return the time-delay information of the line

a. The TS-2669/GCM must be connected to a 115-

under test back to the transmitting point (fig. 3-4). The

or 230- volt ac power source by the power cable at the

modulated carrier produced by the transmitting TS-

rear of the unit. Before doing this, check to make sure

2669/GCM is sent down the test line. At the end, the

the unit is internally strapped for the proper line voltage

signal is demodulated by a receiving TS-2669/GCM and

(fig. 2-2).

the modulation component is remodulated onto a fixed

frequency reference carrier signal produced by the

Caution: The TS-2669/GCM must be

receiving TS-2669/GCM. This reference signal is sent

grounded by the ground terminal on

back to the receiver section of the transmitting TS-

the UP-121/M connector on the

2669/GCM. The signal received at the transmitting TS-

power cable or a shock hazard may

2669/GCM contains phase shifts corresponding to the

result.

delay of the measured line plus the fixed delay

introduced by the auxiliary channel; therefore, relative

b. Operate the POWER switch to ON. Check to

delay measurements can be made on the measured line

see that the POWER ON indicator is lighted. Allow a 1-

section.

With this system, the required delay

minute warmup period.

measurements can be made from the transmitting

c. Operate the REF RETURN-END TO END switch

TS2669/GCM. However, the amplitude characteristic of

to END TO END.

the line under measurement must be made at the

Operate the % MOD-RECEIVE LEVEL-

receiving TS-2669/GCM.

TRANSMIT LEVEL switch to % MOD. Operate the

c. Loop Mode. In the loop method (fig. 3-5), the

MODULATION FREQUENCY HZ switch to the desired

line to be tested is connected at the far end to a second

modulating frequency (25, 83-1/3, or 250 Hz). Note that

line returning the signal to the TS-2669/GCM.

the modulating frequency to be used must be one-

Transmission and reception are conducted at the same

quarter of the lowest carrier frequency to be used or

location, and delay and amplitude measurements can

less, for example:

be made easily. In the loop mode, delay of the forward

and return paths cannot be separated; therefore, it is

Mod freq

Lowest carrier freq to be used

assumed that the forward and return path characteristics

25 Hz

100 Hz

are equal.

83 1/3 Hz

334 Hz

250 Hz

1,000 Hz

3-4