Space Age Sound Machine Circuit

The space-age sound device uses a 556 dual-times IC to produce a phasor sound. That IC is actually two 555 timer ICs in one 14-pin package, as shown in the schematic. Each timer inside the 556 is connected iri an astable multivibrator mode. The first timer has its frequency set by Kl, R2, and Cl. Its output appears on pin 5 and it is coupled through C2 and R5 into the trigger input of the second timer. The second timer has an adjustable frequency that is controlled by PI, R6, and C3. In the second timer, the first frequency mixes with the second frequency and produces the pha-sor-like sounds.
Space Age Sound Machine Circuit - schematic

The output of the second timer, which has the two signals mixed together, is brought from pin 9 through limiting resistor R7 to the input of Ql. The function of pnp germanium power transistor Ql is to amplify the signal to the level that is needed to drive the speaker. The green LED, LI, converts electrons directly into visible photons (light) in time with the pulses from the speaker. The purpose of resistor R8 is to limit the current through the LED to a safe level.

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