Mic Jack Input

[wombol]

Hi guys,

I have a question (2, in fact) about the microphone input on the audio jack. I read somewhere on the interwebs that passing a square wave into standard audio drivers can cause damage, possibly due to the DC levels of the square wave. I am looking to send pulses of square waves (some at ~80Hz, some at 60Hz with varying duty cycles) through the jack, and I am wondering if it is safe to just transmit that wave or whether I should use Digital-to-analogue conversion (DAC) to produce a sinusoidal wave?

On a related note, does anybody know the standard voltage level the mic input should take, as I don't want to damage it.

Thanks everybody,

Sam