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Soft Musical Ringer Circuit Diagram: Build Your Own!
Circuit diagram
The incoming signal is recognized by transistor T1 alongside associated circuitry. Without the incoming ringing voltage, transistor T1 is switched off, while transistor T2 is driven into conduction as resistor R2 is connected to the positive supply lines. Consequently, the collector of transistor T2 is held at a near-zero voltage, thereby keeping integrated circuit IC1 (UM66) inactive. Simultaneously, capacitor C2 accumulates a small positive charge.
Integrated Circuit IC1 (UM66)
Integrated circuit IC1, designated UM66, is a commonly used audio detection device. This IC typically functions as a comparator, comparing two input signals. In this application, it acts as a switching element, triggered by the incoming ringing voltage. Its main function is to rapidly switch the output state based on the comparison of the two input signals. This rapid switching allows for precise control of the audio output, ensuring that the musical tone is activated and deactivated in sync with the ringing signal. It operates with low power consumption, contributing to the overall efficiency of the circuit.
The ringing signal’s positive half activates diode D1, swiftly discharging capacitor C2 to a ground-like potential and cutting off transistor T2, which then biases integrated circuit IC1 (UM66) and applies the audio signal to the base of transistor T3, thereby driving the speaker. During the negative half of the ringing voltage, capacitor C2 does not accumulate charge quickly via resistor R2, so transistor T2 remains non-conducting throughout the ringing interval. This ensures a smooth, musical tone is produced into the loudspeaker, perfectly synchronized with the ringing signal. When the handset is removed from the cradle, the ringing voltage disappears, and consequently, the musical tone ceases.
A warning: Ensure proper grounding of all components to avoid electrical shocks or damage. The design of the circuit is provided by Robert Jones as a source of reference.