I have trouble understanding the operation of the following circuit:
This is the given description of the schematic:
"This is a voltage controlled multivibrator that is used as an acoustic volt meter. The supply voltage is 9 V and the measure range is also 9 V. At the moment when one of the transistors of the multivibrator starts to conduct, the base voltage of the other transistor drops to -9 V. After this, the 10 nF capacitor is charged by the current through the 100 kΩ resistor to around +0.6 V in approximately 0.65 ms, at which point the circuit switches states."
I am not sure what to 1...30V means here. I don't know what sort of multivibrator circuit this is. As I see it, there are 2 switching capacitors, connected in a feedback network, along with two time delay capacitors. I am not sure how to transistors are biased. Also what happens when the left transistor (Q1) is off? I am also not sure what voltage the collector of Q1 does have and how it affects the capacitors' plates (and thus their voltages).