Switches are everywhere. The electrical and electronic push-buttons and clicks are familiar switches. However, there are many other switches that do important work but are usually not perceived as switches.

1. Switches in codes: identify the nature of the signal and the binary states (on and off) of the switche(s) in the following simple code:

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2. Doors and gates as switches: identify the signal and the binary states (on and off) when doors and gates are considered as switches.

3. Biological switches: name at least one biological switch. Identify the signal and the binary states (on and off) of the biological switch.

The strings: S7P5A51 (Physical Change). Can also be S7P5A52 (chemical Change).

The math:
Pj Problem of Interest is of type change (physical or chemical change). A switch allows a stable state to transit into another stable state. We limit our definition to stable states transition eventhough there are instances where unstable states transitions are possible.

1. Function calls; break or exit directives and function instructions constitute the switch-triad in codes. Function calls represent the on state. The break or exit directive represent the off state and the function instructions represent the signals that are turned on or off. Fundamentally, the entire code is a swith-triad where data and functions are turned on or off.

2. The on and off states in doors and gates is easy to identify. Door opens (on). Door closes (off). The signal can be any entity that is allowed to go through the door or gate. The concept of gates is a fundamental concept in integrated circuit design. Smart people have been able to produce very impressive results by assembling numerous electronic gates based on defined values for voltage on and voltage off.

3. The eye-lids. Eye-lids opens (on). Eye-lids close (off). The signal is light. There are other biological switches at play in the cell cycle. The cell cycle is the ordered sequencial events that controls how a single cell divides.

Blessed are they that have not seen, and yet have believed. John 20:29