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.
A pendulum is a small weight on a string or chain. That's it. It can be any weight, and it can be any sort of string or chain. Normally they are small. The weight is normally an object about 1/2 inch by 1 inch in size.