Radar, Gun Laying, Mk. I and Mk. II

Radar, Gun Laying, Mark I, or GL Mk. I for short, was a pre-World War II radar system developed by the British Army to provide range information to associated anti-aircraft artillery. There were two upgrades to the same basic system, GL/EF and GL Mk. II, both of which added the ability to accurately determine bearing and elevation. The name refers to the radar's ability to direct the guns onto a target, known as gun laying.

https://en.wikipedia.org/wiki/Radar%2C_Gun_Laying%2C_Mk._I_and_Mk._II