Detectives shows and phone calls

Have you noticed how many of the old detective radio shows started off with phone calls? That was the standard procedure with the Johnny Dollar series. Also, Sam Spade would start with him calling his efficient secretary, Effie, to tell her he was one the way to dictate his report. And, for at least a portion of the series, Richard Diamond's program would start off with Helen, his sweetheart, calling him at his office. Ting-a-ling, the phone rings, and the show is on!