Dear Mr. Professor, the Exalted One, Pat Townson: In the mid 90s I was an active reader of the Digest and my association still shows in many Google searches [I worked for Digital Equipment at the time]. VAXclusters with food nodes SNAX etc. On of the Portland radio folk today mentioned the early 90s and 900 numbers in his show today. His claim was some television advertisers would encourage you to hold the handset to the phone and the broadcast the tones and actually dial the 900 number. Do I just not remember this or was it never real? I check SNOPES and didn't see a reference. Telcomm has so many references, thankfully. I figured I'd go to the Master! Howard Pierpont Retired DEC/Intel Hillsboro OR[TELECOM Digest Editor's Note: Well, dialing a phone number *accoustically* is certainly sometimes possible; consider the man with his whistle who blew certain tones into the phone to confuse the central office circuitry, or the man who could whistle those tones into the phone. How reliable that method of 'dialing' is I do not know, but if your question is was this a way to defraud telco (at least where 900 numbers and blocks against them was concerned) the answer is no, it was not. If a phone was otherwise equipped to 'dial' a 900 number (many phones have blocks on them against dialing a premium charge number; I know my phones are fixed that way), then whether the tone was 'heard' by the central office via the dial pad on the phone itself or from input via the receiver, central would either accept the request or not. Central does not care if you are a damn fool with a sex hotline or whatever, just that you pay the bill.
This was not the case for the supervisory tones however; they had to be blown into the phone or sent from some external device since telco does not equip your phone with those 'special tones' they use internally. To answer your question, yes I think I heard of that method of dialing also, many, many years ago. PAT]