Maker Factory ELECTRONICS EXPERIMENTS BOX Manual page 271

Circuits 68 and 69: the output is fed back to the base of T1 via R1. R2 and C2 ensure the time delay. If T2 is
electrically conductive, the feedback ensures that T1 also switches through. Then T2 begins to block. That in
turn also blocks T1. As a consequence of this, T2 starts to be conductive and so it continues.
Fig. 3.68: Circuit
68: LED blinker
1 Hz
Fig. 3.69: Circuit
69: LED blinker
3 Hz
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