A catheter is built into an ergonomic handset. Turning the wheel in one direction, the catheter will slide out of the needle into the vein. When turning in the other direction, the catheter will retract while you give RF pulses with the foot pedal. The depth is indicated on the wheel. Every two to three millimeters an impulse is given causing the vein to heat and to coagulate. Since the handset is sterilized with the catheter inside, there is no infection possible because the catheter slides from handset directly into the needle and into the vein.