  VERITAS is an array of four identical telescopes designed for detecting and
measuring astrophysical gamma rays with energies in excess of 100 GeV. Each
telescope uses a 12 m diameter reflector to collect Cherenkov light from air
showers initiated by incident gamma rays and direct it onto a `camera'
comprising 499 photomultiplier tubes read out by flash ADCs. We describe here
calibration methods used for determining the values of the parameters which are
necessary for converting the digitized PMT pulses to gamma-ray energies and
directions. Use of laser pulses to determine and monitor PMT gains is
discussed, as are measurements of the absolute throughput of the telescopes
using muon rings.
