Which type of coupler is known as the British coupler?

The British coupler is known as the G coupler, which is the correct answer. This specific type of coupler is primarily used in the UK and is designed for the secure connection of draft lines in beer service. The G coupler features a mechanism that allows for easy engagement and disengagement from the keg while ensuring that the gas and beer lines are connected properly to prevent leaks or contamination.

Other couplers, such as the M coupler, A coupler, and S coupler, are used in different regions or for specific types of kegs and beers. For instance, the M coupler is often found in German beer service, the A coupler is typically used for European kegs, and the S coupler is used for certain Belgian beers. Each of these couplers has distinct features and configurations that make them suitable for the kegs they serve, but they do not align with the traditional British system, which utilizes the G coupler. Understanding these distinctions is essential for proper beer service and ensuring compatibility with keg types.