Here is The 4 Sound effects generator using UM3561 and a few parts only. It can make siren, Ambulance sirens, Police car sirens, Fire truck siren and Space
SEE! Simple Sine wave oscillator low frequency. Without thermistor and Incandescent lamp so very linear in transistor and zener diode circuit.
This is 60Hz calibration frequency standards for digital clock. As 50hz or 60hz frequency generator at TP 3.579MHZ. power supply 12V.Out put Frequency 60HZ [...]
This is a sample pulse generator using op amp. We often use 555 timer to build a simple pulse generator. The op amp is also easy in oscillator form. More!