Diagram Guide

The tone generator is an astable multivibrator with one of the resistors being variable to change the notes. An amplifier could be used to increase the. volume, but quite a high volume is attained by the astable. Due to the simplicity of the circuit the wave form is rather irregular in shape. (To produce the note. the probe is moved across metal strips wired to points A, B, C etc.)

Simple Musical Organ Circuit


Simple Two-Tone Alarm Circuit Using IC 555

This device gives a two-tone alarm from a digital clock. lt may be used with any CMOS alarm clock chip having an active high alarm output and 1Hz (optional) output. It was built to work with a CT7001 chip and requires no interface components. The 555 operates in normal astable mode when the alarm goes high (ie point (a) approaches VSS). Pin 5 is the normal control voltage input and swings from almost VSS to VDD via the 27K resistor at a 1Hz rate. This causes the audio output to switch between high and low tones, above and below the frequency determined by R1, R2 and C1. To vary the frequency difference, R3 may be altered within wide limits, but it is  inadvisable to keep it below 15K. The basic frequency is best varied by changing C1. Audio output may be varied by changing C3 (depending on  LS impedance). {In the original, a 3552 speaker was used with -12V VDD and was sufficient to rouse an expert heavy sleeper. 

Simple Drum Simulator Circuit

A variety of percussive sounds may be obtained with variations on a simple twin—T oscillator of the type illustrated. The table is given as a guide to the frequency determining and envelope shaping components.