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 bob is the round disk at the bottom of the pendulum and the diameter is the measurement from one side to the other. To select the proper bob size you would need to know the inside width of the clock case. You should have at least 2 inches on each side of the pendulum bob so it can swing in the case without hitting the sides.