 In April 1941 all of the CHL sets were upgraded with a new antenna that was motorized to spin at 1, 1.5, 2 or 3.33 rpm, and used a single transmit/receive antenna instead of separate ones.When first deployed, CHL was used both for early detection of low-level targets, as well as a system for tracking individual aircraft over land; unlike CH which was permanently facing over water, CHL could be turned to look in any direction.This later role became outdated with the introduction of the Type 7 GCI in 1942.