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FINAL TESTS (Using a 48VDC power supply)
Test Equipment Needed (not provided):
• 48VDC power supply
• 1kΩ 5W resistor
• 48VDC voltmeter
• 50VAC voltmeter (only for the ringer test)
Perform the following tests and record the readings obtained in the space provided.
DC TEST
- Refer to Figure 6-20 for the DC test configuration. The oscilloscope is not used for the DC test.
1. Turn the power supply OFF. Connect the 48VDC power supply, 1kΩ resistor, modular jack, and the
telephone as shown in Figure 6-20.
2. Set the ringer switch to ON and position the telephone so that it is off hook (hook switch not depressed).
3. Set the voltmeter to read 48VDC and connect it as shown in Figure 6-20.
4. Turn the power supply ON and adjust it for a reading of 48VDC on the voltmeter.
48VDC
Power Supply
+
1kΩ 5W Resistor
Type A
Type B
Green
Red Red
5. To measure the input voltage to the telephone, connect the negative voltmeter lead to the negative (–) power
supply terminal and the positive voltmeter lead to point "C". The voltage should be between 5 and 12.5VDC.
Input Voltage: _______________
6. To measure the input current to the telephone, measure the voltage across the 1kΩ resistor. Connect the
negative voltmeter lead to point "C" and the positive voltmeter lead to the positive (+) power supply terminal.
The voltage should be between 35 and 45VDC. This indicates that the current drawn by the telephone is
between 35 and 45mA. Resistor voltage: _______________
7. Turn the power supply OFF. Disconnect the voltmeter. Disconnect the 1kΩ resistor and the red wire from
the power supply terminals.
8. To reverse the voltage polarity to the telephone, connect the free end of the 1kΩ resistor to the negative
power supply terminal and the red wire from the modular jack to the positive power supply terminal.
9. To set the power supply voltage, connect the positive voltmeter lead to the positive power supply terminal
and the negative voltmeter lead to the negative power supply terminal. Turn the power supply ON and adjust
it for 48VDC on the voltmeter.
• Variac (only for ringer test)
• Isolation transformer (only for ringer test)
• Oscilloscope (only for voice test)
Green - Type A
Red - Type B
Modular Jack
Red - Type A
Green - Type B
Green
Telephone
Cord
GND
Probe
Figure 6-20
-27-
Telephone
Oscilloscope
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