Back in AM radio days of 60s as the new FM band was making its way to the top it was all the rage to have one of the new multi-band Radios which had AM, FM ,VHF, TV and some times MB Military Band or W Short Wave and when you tuned down into the VHF band to hear Pittsburgh Police you would hear a short twist down dial this repeating message
This is Air Signal Pittsburgh there are no messages at this time.
But then you might hear a message like This air signal Pittsburgh Dr. Johnson you have a message
So what was going on ?
Well it was one of the first Pager services in the country that was run by a lady I meet during a exhibition at now demolished Central Medical Center Hospital.in Pittsburgh's Hill District.
From what I gather the system worked by some one trying to contact a subscriber who would call a special number and leave a message with Air Signal Operator , who then recorded the message which was continuously broadcast over the designated VHF band . The Dr. or CEO who had the receiver would then turn it on between calls and breaks and listen to see if he had a message he would then call special number to retrieve from the operator.
Since the system was such an early use of airwaves I do not know if a tone signal was sent out like more modern pagers to let you know you have a message which is why it kept repeating.
I have searched for and have found no information on this business and will try old business directorys but i have asked numerous people about it and no one remembers it but they do remember hearing the signal but no info on company.