catcher
the catcher
The answer depends on the situation. In baseball, when the catcher signals the pitcher with finger signals, he is concealing his communication from the other team. That is not unethical. Without such justification, the answer seems to be yes.
Yes. A pitcher must make contact with the rubber but it may be a toe, a heel, or the entire foot.
Yes usually white tape so the pitcher has a better view of the signals the catcher is transmitting to him.
I think you are asking what they form. If that is what you want to know, they are called "The Battery," because they work together to try and get the batter out. The catcher makes hand signals for the pitcher to see telling him what type of pitch to throw. The pitcher will either nod or shake his head to let the catcher know if that is the pitch he wants to deliver or not.
Voice signals are analog signals, whereas computer signals are digital .
Hybrid signals are the combination of both analog and digital signals
Here Energy signals are limited but power signals can exist to infinite distance. Non periodic signals are energy signals while power signals are periodic.
Analogue signals are more vulnerable to error than digital signals. See the related question "Why digital signals are more noise free than analogue signals?" for more details.
Closing signals can be verbal or nonverbal
Digital signals