Gotta put in my vote for top favorite: Pluggers Tend To Have 3-digit Phone Numbers.First strip I remember seeing, and, being a part-time/paid-call FF/EMT at the time, it is still hanging over my workbench.
I used to install and maintain pay phones and line lines back in the day when you rented the instrument from the phone company, and service was rated on 2-hour outage restoration and 12 hour other repairs – free.
Later in life, we sent rookie telephone switch room techs for a bucket of dial tone.