Gas-tube protector units are used in telecom network interface device boxes and central office switching gears to provide protection from lightning and alternating current power cross faults on the telecom network. Current gas discharge tube (GDT) protector units are unreliable from the standpoint of mean turn-on voltage and run-to-run variability. Molybdenum electrodes with various interlayer materials were coated with single-walled carbon nanotubes and analyzed for both electron field emission and discharge properties. A mean direct current breakdown voltage of 448.5 V and a standard deviation of 4.8 V over 100 surges were observed in nanotube-based GDTs with 1 mm gap spacing between the electrodes. The breakdown reliability is a factor of 4–20 better and the breakdown voltage is ∼30% lower than the two commercial products measured. The enhanced performance shows that nanotube-based GDTs are attractive overvoltage protection units in advanced telecom networks. © 2000 American Institute of Physics.