What is a requirement for all draft beer dispensers aside from temperature maintenance?

Maintaining keg pressure and ensuring the dispenser is easily cleanable are crucial requirements for draft beer dispensers beyond just maintaining temperature. Proper keg pressure is essential for preserving the quality and carbonation of the beer, which directly impacts the taste and overall drinking experience. If the pressure is too low or too high, it can lead to issues like flat beer or excessive foaming, both of which detract from the beer's serving quality.

Additionally, the ease of cleaning is vital in draft beer systems. Beer can leave residues that, if not properly cleaned, may cause contamination or affect the flavor of future servings. Regular cleaning helps prevent microbial growth and maintains hygiene, ensuring that every pint served is fresh and of high quality.

Other options, while they may describe certain features of beer dispensers, do not represent universal requirements. For instance, not all dispensers are required to be fully enclosed, have glass windows, or be mobile; these features can vary based on model and design preferences but do not impact the fundamental requirements for optimal beer dispensing.