Abstract: A system for hermetically sealing a thermoplastic tube during each cycle of operation of the system. A hand-holdable sealing gun has a pair of electrodes between which a tube to be sealed is placed. One of the electrodes is fixed and the other is moved by the core of a solenoid on which the moveable electrode is mounted. An RF field is established between the two electrodes to heat the tube between them. A limit switch is closed to terminate the RF field when the distance between the electrodes reaches a predetermined minimum distance. A trigger switch on the gun when squeezed initiates a cycle of operation of the system. A power supply, a source of RF energy, a mode switch and a second trigger switch are mounted in or on a housing. A bracket is also mounted on the housing for the sealing gun. The bracket positions the gun so that it can be operated in a fixed position.