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Many people enquire to find out how to wire an LED into the bell ringing
circuit of a UK phone. In the past the phone would have been fitted
with a neon lamp, but now-a-days that it not achievable.
Some also want to
operate a relay from the ringer. The advice here is to use an Opto
Isolator to ensure separation from the telephone line.
Connections:-
- Inside a 700 type telephone - connect to terminals 4 and 16 in a
correctly converted telephone.
- In a Line Jack Unit - connect to 3 and 5.
LED that flashes in sympathy with ringing
Build the circuit as shown in the picture below. Then connect either
to the line jack or inside the telephone.
|
Part |
Quantity
|
Description
|
| R1 |
1 |
10K 1/4 W Resistor |
| D1 & D2 |
2 |
20V 1/4W Zener Diode |
| D3 |
1 |
1N4148 Diode |
| LED |
1 |
|
Relay that operates in sympathy with ringing
Build the circuit as shown in the picture below. Then connect either
to the line jack or inside the telephone.
|
Part |
Quantity
|
Description
|
| C1 |
1 |
0.47uF 250V Capacitor |
| R1 & R2 |
2 |
10K 1/4 W Resistor |
| R3 |
1 |
1K 1/4W Resistor |
| D1 & D2 |
2 |
20V 1/4W Zener Diode |
| D3 |
1 |
1N4148 Diode |
| Q1 |
1 |
2N3904 or 2N2222 NPN Transistor |
| U1 |
1 |
4N27 Opto Isolator |
| RELAY |
1 |
Solid State Or Regular Relay |
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