TRAFFIC CONTROL TELEPHONE SYSTEMS Circuit - Sam Hallas

Operate CVK, note meter reading on the 70-volt scale, and if necessary
operate range key so that reading is near 25 volts.
Note this reading, and check the test battery voltage by operating SCK.
The resistance multiplied by 1, 10 or 100 can then be determined from the
appropriate curve on the chart, or by interpolating between curves (Fig.
22).
Resistance by Voltmeter Test
Fig. 21.
7. Line Resistance Measurements by Voltmeter Method. (See Fig. 21.)
If the resistance to be measured is fluctuating (line leakage in wet
weather for instance), if may be difficult to obtain a balance on the
Wheatstone Bridge, and a voltmeter test, which will show the fluctuations,
may be preferred.
To measure the Line Loop Resistance. Insert test plugs into the line to
be tested then proceed as in paragraphs 6 or 7.
8. Line to Earth Measurement by Voltmeter Method. (See Fig. 21.)
Insert plugs into line to be tested. Operate CVK and EAK for measuring
"A" line to earth, or EBK for measuring "B" line to earth, and proceed
as in paragraph 6 except that the test battery voltage should be checked
before the earth test keys are operated.
9. Measurement of Incoming Volts from Line.
Insert test plugs into appropriate line, operate LVK, CVK and RAK,
read voltage on the 70-volt scale of meter. N.B.— If CVK is operated
without LVK, the 50-volt test battery will be connected in series with the
incoming voltage.
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