A syphon is commonly used to protect which device?

A syphon, often referred to as a syphon tube or trap, is specifically designed to protect pressure gauges from direct exposure to high temperatures or steam that can cause damage or inaccurate readings. When installed, the syphon creates a barrier that allows condensate to form in the tube, which in turn helps to cool the steam or hot fluid before it reaches the gauge. This is essential because high temperatures can lead to the failure of the pressure gauge due to overheating, which can compromise its functionality.

The syphon's role in cooling the pressure gauge ensures that the readings remain accurate and that the device continues to operate effectively in varied thermal conditions. This is why the correct answer identifies the pressure gauge as the device protected by the syphon.