Microphone voltage on a 3,5mm PC microphone/headphone jack
Taking the Android specifications, you need 2.2Volts in series with a 2.2K resistor.

Like this example from the Android specs:



You can probably use 3V (2 AA Cells of 1.5V each.)  5Volts through that 2.2K probably won't hurt anything either.



Example for using Scope:







simulate this circuit &ndash; Schematic created using CircuitLab