This electronic timbre can be made smoothly dog bell for door and gives us every chance of amendmen

This electronic timbre can be made smoothly dog bell for door and gives us every chance of amendment, as the sound is concerned. The circuit consists of an astable multivibrator implemented: - A timer 555 - A decade dog bell for door counter CD4017 dog bell for door - A UJT transistor oscillator - A bipolar transistor (BJT) as a power amplifier to the speaker.
The relaxation oscillator having a frequency which depends on the values of C2 and R14 plus the value of the corresponding potentiometer connected to each of the outputs of CD4017 E ring generates nine notes, fully manipulable with nine potentiometers varying the frequency at Rocking UJT. The operation of the circuit astable multivibrator send its output signal to the clock input of the decade counter (leg 14). The CD4017 clock input will always be enabled and when the leg 15 (RESET) of the integrated circuit is in low level. For practical purposes, this is our doorbell button. (PB) While pressing dog bell for door the doorbell is pressed, the decade counter outputs deliver on their high level sequentially. (See figure) Each output enables UJT relaxation oscillator with a different value (potentiometer R14 +). As the potentiometers are modifiable, the oscillation frequency for each output CD4017 output of the relaxation oscillator, taken from the junction of R13 with transistor UJT were amended, applies to the base of the bipolar transistor that feeds the speaker. To change dog bell for door the speed at which sound the nine notes, one can vary the output frequency of 555. This is achieved by changing the values of resistor R2 and capacitor C1 BOM - Resistors: dog bell for door R1 470K, 220K R2, R3 15K, 10K R14, R13 150 ohms R15 220 ohms. - Potentiometers: 9 100K - Capacitors: C3 100uF/12V, 1uF/250V C1, C2 47nF/250V - Diodes 9 1N4148 or 1N914 - Transistors: 2N2646 T1, T2 2N2222 - IC: IC1 NE555, IC2 CD4017 - Other : momentary contact button (PB), 1 miniature 8 ohm speaker extracted from www.unicrom.com
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