AT&T Bell System Plant Series Alignment Instructions page 9

SECTION 107-302-500
scribed below, since it checks the signal only as
far as the input to the data demodulator.
(a) Adjust the output power of the 600-ohm
balanced oscillator (OSC jack) to -24
±1 dbm.
(b) Connect oscillator to MON cord through
circuit of Fig. 1 or use 906 OSC IN and
MON TEST jacks. Connect a terminal test
'? ..
)rd to the 906 DEMOD INPUT MEAS jack.
Operate key SUPV-DATA to DATA and block
operated key DATA READ.
(c) Set oscillator frequency to 740 ±20 cps
and CHAN SEL switch to 1 and hold
op-
erated key TMR-SND LEV to TMR. (Relays
DDC, TMC, and CHl are operated.) On the
transmission measuring set, read -19 ±3 db
for an oscillator output of -24 dbm.
(d) Release key TMR-SND LEV and hold op-
erated key FRR-FRS CHK to FRR. Read
2125 ±20 cps on the electronic counter. Re-
lease key FRR-FRS CHK.
(e) Repeat (c) and (d) for the following fre-
quencies and settings of the CHAN SEL
switch:
CHAN SEL
CPS
Relays
Operated
2 1218
DDC, TMC, CH2
3 1695
DDC, TMC, CH3
4
2173 DDC, TMC, CH4
5 2650
DDC, TMC, CH5
6 3128
DDC, TMC, CH6
(f) Set switch GEN SPEED to each of its po-
sitions. Each time the position is changed,
momentarily release the DATA READ key. For
each position, the lamps corresponding to the
switch setting should light.
(g) When finished, return all keys to normal.
4.27
A detailed discussion of the location of
causes for failure of the above test is given
in 5.31 through 5.36. If any of the measured fre-
Page 14
frequencies is wrong, there is an error in the
carrier frequency being supplied from the Bl data
carrier supply unit. (See 4.56.) If any of the
measured powers is wrong, make sure that 4.22 is
satisfied. If the trouble remains, see 5.32 through
5;35. If no signal gets through at all, see 5.32
through 5.34. The operation of the relays may be
checked from SD-73022-01, Sheets B7 and B6.
4.28
If the set fails to measure distortion satis-
factorily on Bl system tests even though
working on local test ( 4.15) and the above test,
there may be troubles in the channel demodu-
lator. (See 4.35.)
CIRCUIT FOR MEASUREMENT OF DISTORTION
ON 4-WIRE WIDE-BAND CIRCUIT
4.29
The signal from the 4-wire facility is con-
nected to the input of the data demodulator
by the DMC relay. The output of the demodu-
lator goes to the distortion measuring circuit,
and the data distortion is measured as in 4.01
through 4.08. The operation of the Fl relay which
controls the frequency of the demodulator is
controlled by the F lead. Assuming the tests of
4.15 through 4.17 work, these functions may be
checked by the following test.
(a) Connect a front terminal test cord to a
line drop (LD) cord and ground the
sleeves of the cords. This can be done using the
BRIDGE GS jacks in the 20A if they are avail-
able.
(b) Operate keys and switches as follows:
(1) DATA-SUPV to DATA
(2) WBFl to WBFl
( 3) SND-TMS to SND and block operated
(4) DATA READ block operated
(5) TST-DMO to TST
(6) GEN MODE to RDM
(7) GEN SPEED to 150
(8) LEV OUT to LO
(Relays A, B, C, GSl, GS3, F, DMC, DDC, and
TMC are operated.)