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SECTION 5 - EQUIPMENT NEEDED
Tools Needed (not provided)
Long Nose Pliers
Diagonal Cutters
Note: The following equipment is not included unless indicated.
Testing Equipment Needed:
The test procedures are written for using AC and DC power supplies (only for final ringer test) or a 9V battery.
If you don't have a power supply for the ringer, transmit-receive and dialer tests, you can use a 9V battery.
Using a 9 Volt Battery
• 9 volt battery
• Battery Snap (Included)
SECTION 6 - ASSEMBLY INSTRUCTIONS
RINGER
Circuit Description - The ringer circuit is connected directly across the Tip and Ring inputs (see Schematic
Diagram). The capacitor C1 blocks the 48VDC that is present on the inputs when the phone is on the hook. To
signal an incoming call, the Central Office places a 90VAC 20Hz signal on top of the 48VDC. If the ringer switch
(S1) is closed, transistor Q1 conducts during the 1/2 cycle that the Ring terminal is positive. The collector to
emitter voltage is applied to the buzzer causing it to change dimensions. The feedback lead is connected to the
base of transistor Q1 through resistor R7 causing the circuit to oscillate at about 3kHz. There is no oscillation
during the negative portion of the 20Hz signal. The buzzing sound is thus produced by the buzzer changing
dimensions at 3kHz during the positive portion of the 20Hz ringing signal.
The four neon bulbs LP1 through LP4 and resistors R1, R2, R3 and R4 are also connected across the Tip and
Ring inputs. When the ringing signal causes the voltage across the bulbs to exceed about 100 volts, the bulbs
conduct, giving a visual indication of the incoming call.
Phillips Screwdriver (small point size)
Small Pencil Type Soldering Iron
of 25 - 40 Watts
Using Power Supplies
• 9 - 48VDC Power Supply
• Resistor 1kΩ 5W
• Voltmeters 48VDC and 50VAC
• Oscilloscope
• Variac
• Isolation Transformer
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