City-wide personal signaling at allentown-bethlehem, pa

In the Allentown-Bethlehem area of Pennsylvania, the strange sound of a low whistle issuing from the coat pocket of a pedestrian (who will, on hearing it, probably seek the nearest telephone and dial a number) might be mystifying to the uninitiated. But to the pedestrian from whose pocket the whistle actually came, it represents a new Bell system telephone service that for some time has been functioning in this area.