RS232 is probably one of the most used, easy to develop and easy to apply communication protocol. We generally encounter to this standard at the MCU applications. But it has some restrictions.
http://www.circuit-projects.com/converter-circuits/rs232-rs485-converter-with-automatic-rx-tx-control.html
This circuit is intended to provide good square waves converting a sine wave picked up from an existing generator. Its main feature consists in the fact that no power source is needed: thus it can be simply connected between a sine wave generator and the device under test.
http://www.redcircuits.com/Page17.htm
Here is a power supply which makes about +30V from +5V power supply.
http://www.interq.or.jp/japan/se-inoue/e_ckt27.htm
Portable Power for the Future. LT Application Note.
http://www.linear.com/pc/downloadDocument.do?navId=H0,C1,C1003,C1042,C1143,C1083,P1787,D5598