Complex sentence: This separate second-stage regulator and hose, or "alternate air source", "safe secondary" or "safe-second" for short, is typically yellow in color, signaling that it is an emergency or backup device.
Split into simpler sentences: This separate second-stage regulator and hose is also known as "alternate air source", "safe secondary" or "safe-second". It is frequently yellow in color, signaling that it is an emergency or backup device.