This Telephone bell ringer circuit for generating the electricity bell in the old telephone. This circuit is relatively loud. so can use to replacement the same ringer or the original telephone may be lost. We do not need a new phone. This circuit is easily to build, because it uses a single IC as shown in figure below. Before you read working this circuit. I suggest a simple ideal is: Detect ringing signal tone with light and sound The detect ringing signal tone circuit with light and sound.It is easy to use and good quality, Do not enter the power supply. Which as Detect ringing signal tone circuit Or ring tones on the telephone line, a signal incoming calls. When an incoming call,When an incoming call, The C1, C2, will act as a coupling signal AC Volt to diodes D1, D2.Signal voltage is reduced down to approximately 10V.By D2 to detect, only a negative signal,One extreme to the other end of the wire loop.The D1 detect a positive signal, and the 4 LED. Flashing light attached to it,with frequency of the ringging tone.Which is about 20 Hz. and piezo speaker, show the audio beep .. beep, followed by a tone frequency of the ringing. LED can be connected in series to increase, but less in proportion to the light.The circuit uses power from the telephone line. How this circuit works The called signal from the telephone lines is entered through C1, R1 Come to the bridge diode circuit D1-D4, D5 is the positive voltage at 20V supply to pin 1 of IC1 that KA2411 or CS8205 as the Telephone Bell Replacement IC. When IC1 is given the supply volt as I said, it will generator a ringing signals through the R5, to drive the Piezoelectric transducer BZ1 be a bell tone out to hear. The ringing tone light, we may reduce the R5 for low down. We hear the sound of the Oscillator 2 series, which differ by the output frequency chops to be a frequency generator circuits. Which consists with R3, C3 is low. F-LOW = 1/1.289 R3.C3 For a maximum frequency is calculated from. F-h1 = 1/1.504 R4.C4 The second highest frequency is calculated from F-h2 = 1/1.203 R4.C4 The parts of circuit IC1__________KA2411 or CS8205___Telephone Bell Replacement IC D1-D5________1N4007___1000V 1A Diodes ZD1__________20V 0.5W Zener Diode R1__________5.6K 1/2W Resistor R2__________12K 1/4W Resistor R3__________100K 1/4W Resistor R4__________390K 1/4W Resistor R5__________820ohm 1/2W Resistor C1___________1uF 250V Polyester Capacitor C2_________10µF 25V Electrolytic Capacitors C3___________0.22uF 63V Polyester Capacitor C4___________0.0022uF 63V Polyester Capacitor C5___________0.1uF 63V Polyester Capacitor BZ1__________Piezoelectric Transducer How to builds You can builds this projects with make the PCB before and then puting All components in this circuit (as Figure 2)except of the piezoelectric transducers can be assembled into a perforated board. You should check the accuracy. Then try to connect the telephone lines, then call come in, will be have hear the ringing tone, if the sound is not impressive, you can change the RC with formula given above.