Hi Michael !

    The Lectron set makes experimenting fun and always challenging.
    I like to take classic circuits (like the Schmitt trigger) and create something completely new around this !

    Has anyone figured yet out how the oscillations occur ?

    Well here’s some explanation :

    First, the capacitor starts to charge via R2 and P1.
    As soon as the level of the Schmitt trigger is reached, the output of T2 goes HIGH (negative voltage – PNP transistors !) and thus driving T3 to make the lamp go on.
    As T2 blocks, the voltage across R7 drops.
    This causes the E of T1 going more positive (PNP transistors !). The gain of T1 rises and this is speeding up the process of the Schmitt trigger.

    But now, the capacitor will discharge through the B-E junction of T1 and R7 quite rapidly.

    This causes the Schmitt trigger to return to start position.

    Many greetings,