AT&T Bell System 1097A Description And Use

BELL SYSTEM PRACTICES
AT&TCo Standard
SECTION 634-020-505
Issue 1, May 1975
1097A FILTER
DESCRIPTION AND USE
1. GENERAL
1.01
The 1097 A filter (Fig. 1) is a narrowband
filter designed for use with the 147C amplifier.
This permits toning and pair identification where
noise
01·
power influence is a problem. The 1097 A
filter will filter out power line interference and
other electrical noise while amplifying the test tone.
1.02
The 1097 A filter is precisely tuned to a
frequency of 577 .5 Hz. The filter must be
used ONLY with a precision tone source such as
found in the KS-14103 L6 breakdown test set or
the 138A test set. IF USED WITH ORDINARY
TONE SOURCE, UNSATISFACTORY AND
INTERMITTENT OPERATION WILL RESULT.
1.03
Section 634-200-450 covers the use of the
138A test set.
2. DESCRIPTION AND USE
2.01
The 1097 A filter is housed in a molded plastic
case 1 1/2 inches by 1 3/ 4 inches by 3 3/ 4
inches and weighs approximately 1/ 4 pound. A
cord and plug assembly is permanently attached
to the filter. The filter snaps on the side of the
147C amplifier and plugs into the amplifier REC
jack. The filter is provided with an output jack
for connection to a headset.
2.02
The 1097 A filter contains no batteries but
is powered from the 147C amplifier through
the REC jack. Both units are turned on by plugging
the 1097 A filter into the REC jack of the 147C
amplifier as shown in Fig. 2. Operation of the
1097 A filter requires a 147C amplifier because the
147B amplifier DOES NOT supply the necessary
battery voltage. TO CONSERVE THE BATTERY,
UNPLUG THE 1097 A FILTER FROM THE 147C
AMPLIFIER WHEN THE UNITS ARE NOT BEING
USED.
2.03
The output of the tone source and the gain
of the amplifier must be adjusted to obtain
the best performance of the amplifier-filter combination.
SNAPS FOR
ATTACHING
TO 14 7C
AMPLIFIER
PLUG FOR
CONNECTION
TO 147C
REC JACK
Fig. 1-1097A Filter
The recommended method is to first adjust the
gain of the 147C amplifier while listening to the
noise level directly out of the amplifier before the
1097 A filter has been inserted. The tone source
may or may not be attached to the pair to be
tested, but only the noise level is important for
this adjustment. The pickup device (probe or
exploring coil) connected to the input of the 147C
is placed near the cable and the gain adjusted until
the noise level at the headset is loud or until
saturation occurs. The gain is then adjusted back
to one-half this value and the 147C amplifier is
ready to operate.
2.04
Next, the tone source is adjusted for a low
level, usable tone at the headset with the
1097 A filter connected. If tht! tone is to be applied
at a remote location where adjustment is difficult,
©
American Telephone and Telegraph Company, 1975
Printed in U.S.A.
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