LED THAT FLASHES WITH RINGING


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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Last revised: November 20, 2021

FM