Image: circa 1939 on Ventura Blvd. at Lankershim Blvd. in North Hollywood.
The Acme traffic signal was manufactured in Los Angeles beginning in the 1920s. See more of these kinds of signals at http://www.pulpinternational.com/pulp/entry/Assorted-photo-of-Acme-semaphore-traffic-signals-from-Los-Angeles.html .
See a modern video of a restored Acme signal: https://www.youtube.com/watch?v=ooF9il6DZ-w . The bell rings, the semaphore blades move and the lights illuminate in sequence.