Soft Musical Telephone Ringer by UM66T

Posted on Feb 6, 2014

The incoming ring is detected by transistor T1 and components wired around it. In absence of ringing voltage, transistor T1 is cut off while transistor T2 is forward biased as resistor R2 is returned to the positive supply rails. As a result collector of transistor T2 is at near-ground potential and hence IC1 (UM66) is off. Also capacitor C2 is ch

 Soft Musical Telephone Ringer by UM66T
Click here to download the full size of the above Circuit.

arged to a slightly positive potential. During positive half of the ringing voltage, diode D1 forward biases transistor T1 and rapidly discharges capacitor C2 to near ground potential and cuts off transistor T2 which, in turn, causes IC1 to be forward biased and music signal is applied to base of transistor T3 which drives the speaker. During negative half of the ringing voltage, capacitor C2 cannot charge rapidly via resistor R2 and hence transistor T2 remains cut off during the ringing interval.

Leave Comment

characters left:

Related Circuits

  • New Circuits



    Popular Circuits

    Linear optocoupler for instrumentation
    Micropower double ended limit detector
    Geiger Counter Ii Circuit
    Voice link over spread spectrum radio
    Simple Emergency Lamp
    Muscular Bio stimulator
    Single transistor audio mixer
    555 Momentary Switch Circuit
    Circuit Crystal Oscillator/Amplifier
    Digital Theremin
    FGDF-3 three-phase low-temperature iron plating power supply circuit