It is a relatively simple circuit, with which we can have optical and sound clue, when we have telephone ring in the line of telephone. The calls in the line, are changed in pulses of frequency 400 HZ from the IC2, in exit 3.
Then via the IC4, after they are strengthened at two times, they can be drive to the entry of amplifier and a loudspeaker, so that we hear the ring, in what level we want. The desirable level of sound is regulated by the trimmer TR1 that if we want can be replaced with pontesometer. With the led LD1 we have optical clue, of rings. Simultaneously via the IC3 it can become control, exterior circuit, adapted in the needs each virtuous.
R1-3-13=4.7Kohm C1-7 =100nF 630V Q1-2 = BC550C
R2-11-12 =1Mohm C2=4.7nF 63V MKT IC1-3 =4N35 – CNX38
R4 =1Kohm C3 =220uF 25V IC2=LM555
R5 = 2.2Kohm C4 =33nF 63V MKT IC4 =TL071
R6 = 33Kohm C5 =220nF 63V MKT LD1 =LED 3-5 mm
R7 =390Kohm C6 =10uF 25V TR1=10Kohm Trimmer or Pont.
R8 =820ohm C8 =47nF 63V MKT CON1 =4 pin connector
R9 =22Kohm C9 =100uF 25V CON2 =4 pin connector
R10 =1.8Kohm D1-2 =20V 1,3W Zener
R14 =10Kohm D3 = 1N4002 .
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