Universal integral type 555 timer has another use -- in cheap musical synthesizer that plays a musical phrase from simple songs. It uses two timers: one generates the rhythm, and the other generates tone signals.
The circuit shown in the figure, performs the functions of the audible alarm in the phone, it plays the first 10 notes of the song "a Pretty girl is like a melody". When connecting the control input of timer 1 to the supply voltage Vcc melody is repeated continuously.
(click to enlarge)
The frequency of the tone for the song "a Pretty girl is like a melody"
Account
Tone capacitor, µf
Frequency, Hz
0
0,042
329
1
0,040
349
2
0,038
370
3
0,033
440
4
0,038
370
5
0,036
392
6
0,034
415
7
0,033
440
8
0,027
523
9
0,033
440
Music synthesizer, assembled on two integrated timers, plays a simple song from 10 notes Timer / sets the rhythm of the melody, and the timer 2 generates tone signals. When connecting the control input of the timer to the power bus, the melody is repeated continuously. The switch position "Style" is defined sharp or smooth transitions between notes.
Firm General Telephone and Electronics (Clearwater, NJ Philadelphia, PA)
Literature
Publication: N. Bolshakov, rf.atnn.ru