Combining NPN and PNP transistors in one electronic circuit (demo)

Correction to the video: right working voltage is 4,0 V - 4,5 Volt (critical). Demo about how to combine NPN and PNP transistors in one (switch) circuit. Very basic principles, especially for switch applications. Here a demo with a non stabile Muvib (switch) that drives a bicycle lamp. NPN must be driven with a + voltage on its base, PNP must be driven with a - voltage on its base. For audio amplifiers (linear mode amplifier) this differs of course, but it is useful to keep these principles in mind. More circuits in my books on the Lulu website, author Ko Tilman. LINKS TO INFORMATIVE & GENERAL VIDEOS ABOUT ELECTRONICS What do you need for an electronic lab? https://youtu.be/v503bmymCWw How to test a power supply https://youtu.be/BeNoSmm3D_4 Elementary electronics, the bipolar transistor part 1 https://youtu.be/6tBdTzv3ENM Elementary electronics, the bipolar transistor part 2 https://youtu.be/maGOrqh_5-Q Elementary electronics: coils https://youtu.be/Lbb5nvlY0TE Elementary electronics: how to damage a bipolar transistor immediately (VERY important) https://youtu.be/VkeNKFqgsko The most important properties from bipolar transistors https://youtu.be/-mTjz4E5ua8 Prevent transistor leads from breaking https://youtu.be/iEe37oz4tww Combining NPN and PNP transistors in 1 circuit https://youtu.be/jfchBvkM4YA How to make a standard NPN Darlington https://youtu.be/D_WzRkFCCyo What to do with a transistor Darlington https://youtu.be/FrT395Nf6HI How to drive a relay by means of a transistor or Darlington https://youtu.be/R7cvddqVn18 Discriminating European transistor types https://youtu.be/LnpdBI3kJOE 2N3055 with a too low amplification factor, throw them away ? https://youtu.be/y_eW6xLiOKM The importance from the emitter capacitor in a grounded emitter transistor circuit https://youtu.be/br8iXVXRVl4 The transistor series regulator practice (hum suppressor!) https://youtu.be/YL41FPH_H-s How to make a shunt – DC ampèremeter https://youtu.be/FN59W9SGou4 Diodes, their voltage drop and its practical application https://youtu.be/vBv49BDznIA Passive diodes testing (barrier voltage) https://youtu.be/EI0-fj--Jjk Passive diode testing part 2 (capacitance-barrier layer) https://youtu.be/oKIcbubaUWw Point contact diodes https://youtu.be/Hgxm37foGww Electron tubes, some basics https://youtu.be/5a0NnfjGQw0 Do our ears make harmonics? https://youtu.be/2909D9o-Rs4 Oscillation conditions https://youtu.be/AaGDpreMdM8 Oscillation conditions part 2 https://youtu.be/efW6br21Jbc Effect of temperature changes on a VFO https://youtu.be/xvpqlv_rA6g Voice pattern, square waves, triangle waves, harmonics https://youtu.be/xDjox3vfpms 741 Sine wave (Wien Bridge) 0scillator-typical problems https://youtu.be/PwfK0K7NY9c Oscillators, how they can confuse you and disguise https://youtu.be/SQpTrM9l0Sc Why an oscillator? https://youtu.be/Ahrtsggn_EY L-C filter/transistor and how to create useful waveforms https://youtu.be/wV41_FZ9eGs Changing/restoring waveforms with a R-C or L-C filter/dif