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.
Until fairly recently there was only one thing that was exactly one meter long. It was the prototype meter, a rod of platinum that was by definition exactly one meter. The unit itself was originally based on the length of a pendulum that swings with a given frequency, so it wasn't chosen based on some every day object of the given length.