Path: utzoo!attcan!uunet!samsung!sdd.hp.com!hp-pcd!hpcvra.cv.hp.com!rnews!hpcvbbs!akcs.markl48
From: akcs.markl48@hpcvbbs.UUCP (Mark Allen Louwerse)
Newsgroups: comp.sys.handhelds
Subject: Re: Dual tones for HP28S (and HP48)
Keywords: HP28S dual tones
Message-ID: <27666be0:926.5comp.sys.handhelds;1@hpcvbbs.UUCP>
Date: 12 Dec 90 18:40:13 GMT
References: <1990Oct17.210043.19196@rodan.acs.syr.edu> <1990Oct23.182155.15578@
Lines: 14

This has also been a question of mine.  While in high school ten years
ago, when I was cutting my teeth on Commodore PET BASIC, I stumbled
across a magazine article that programmed a TRS - 80 to dial a
telephone(tone).  I don't know how they did it exactly, but somehow they
combined the two frequencies mathematically (an average or a hormonic of
the two frequencies) and used them on the single tone generator of the
TRS - 80.  By the way, program your 48 or 28 for a long tone, 1 to 5
seconds long. Now stick the calculator to your ear(no offense!).  On the
48, for me anyway, the tone gets pretty loud when my ear is against the
card cover(for the ROM and RAM cards).  Anyway, if anybody knows anything
about the article or the math formula let us know!

                                       Mark Louwerse -markl48
                                       Cedar Rapids, Iowa