Circa 1937 – In all my internetian wanderings through photos of L.A., I’ve never seen one of these raised booths before. It stood on Main St in downtown L.A. looking north from Ninth to where Spring and Main converge. These were manually operated traffic lights in use in L.A. The semaphore lights were called ACME and the booth was a manned traffic tower that could send information back to a main control center to allow the whole ACME timing system to be adjusted to meet the fluctuations in daily traffic flow. You can see additional STOP / GO signal on top of the booth. An underground control room beneath Pershing Square managed the ACME System bounded by 1st, 9th, Hill and Main Streets. Apparently, the operator also had a megaphone and would yell at jaywalkers who were trying to catch a street car in the middle of the block or while it was negotiating the corner.