See: http://vintagraph.com/collections/wwii-posters/products/keep-it-alive-for-national-defense

This WWII-era poster from Consolidated Edison System Companies shows a lineman working on a telephone pole with the message: "Keep it alive! For National Defense." Illustrated by Weimer Pursell. Keep it alive for national defense was one of a large number of patriotic posters created during WWII to motivate workers as the nation mobilized war production.

I first noticed this when Shorpy posted it to Facebook. http://www.shorpy.com/search/node/vintagraph