  The recently approved India-based Neutrino Observatory will use the world's
largest magnet to study atmospheric muon neutrinos. The 50 kiloton Iron
Calorimeter consists of iron alternating with single-gap resistive plate
chambers. A uniform magnetic field of $\sim$1.5 T is produced in the iron using
toroidal-shaped copper coils. Muon neutrinos interact with the iron target to
produce charged muons, which are detected by the resistive plate chambers, and
tracked using orthogonal pick up strips. Timing information for each layer is
used to discriminate between upward and downward traveling muons. The design of
the readout electronics for the detector depends critically on an accurate
model of the charge induced by the muons, and the dependence on bias voltages.
In this paper, we present timing and charge response measurements using
prototype detectors under different operating conditions. We also report the
effect of varying gas mixture, particularly $SF_6$, on the timing response.
