Maker Factory ELECTRONICS EXPERIMENTS BOX Manual page 308

Circuit 157 to 163: T1 and T2 form a sensitive bistable amplifier. A feedback is triggered with C1 (C2). The time
delay is determined by the combination R1/C1 (C2). This way, cyclical fast tipping processes are triggered..
310
Fig. 3.160: Circuit
160 – Needle pulse
generator 500 Hz
Fig. 3.161: Circuit
161 – Needle pulse
generator 2 kHz