Is it that the "earphone" that you want to use as a mic? If so, the thing wired across it is a "limiter", which is like a bi-directional Zener with very soft knees... It is only useful to prevent blowing your ear drums, so leave it out... If you yell into the earphone, it will work like a dynamic mic, and generate a small voltage without any batteries, resistors, or capacitors.
If it is the carbon mic that you want to use, the question is WHY? They sounded like crap when they were invented, and still do. Get an electret or dynamic.