Maker Factory ELECTRONICS EXPERIMENTS BOX Manual page 284

Circuit 105 and 106: Capacitor C1 ensures the time delayed feedback from the output (T1 emitter) to the input
(base T2). The two transistors switch each other on in cycles. The process starts with S1.
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Fig. 3.104: Circuit 104 – Discharge circuit for AA batteries
Fig. 3.105: Circuit
105 – Whistle buoy