Signal Quality. Spektrum telemetry modules keep tabs on the quality of the signal coming to the receiver and send this information back to the transmitter where it is represented on the LCD screen using a familiar signal bar scale.
A pendulum is a weight suspended from a pivot so that it can swing freely. When a pendulum is displaced sideways from its resting, equilibrium position, it is subject to a restoring force due to gravity that will accelerate it back toward the equilibrium position.
Ballistic pendulum. A ballistic pendulum is a device for measuring a bullet's momentum, from which it is possible to calculate the velocity and kinetic energy. Ballistic pendulums have been largely rendered obsolete by modern chronographs, which allow direct measurement of the projectile velocity.