 Q2 collector voltage is the output of the circuit (in contrast to the astable circuit, it has a perfect square waveform since the output is not loaded by the capacitor).When triggered by an input pulse, a monostable multivibrator will switch to its unstable position for a period of time, and then return to its stable state.The time period monostable multivibrator remains in unstable state is given by "t" = ln(2)"R"2"C"1.