At 02:58 PM 10/30/98 -0500, you wrote:
>>  BSI and BSII Stamps from parallax are PIC based chips (16c56-16c57). They
>> generate DTFM signals using a simlpe instruction (PBasic) without additional
>> ICs or special telephone chips associated to the hardware.
>>
>>  DTMFOUT 3,300,200,[6,5,4,2,0,3,0]
>
>
>>That's nice, but do they give you a reccomended filter to achieve the
>>spectral purity required by the FCC??
>
 I think so,...
 "*Commercial* designs that interface electronic devices to the phone line
normally require the approval of the  Federal Communications
Commission(FCC)to ensure the quality and reliability of telephone service.
 Manufacteres of phone accesories often take the shorcut of using an
offf-the-shelf interface,known a a Data Access Arrangement (DAA).
Since the DAA has already been checked out by the FCC ,it's generally much
easier to get a DAA-based design approved than a from-scratch circuit.
Unfortunately,DAA tend to be somewhat expensive in small
quantities($25+each),and are sold primarily through high-volume
distributors geared toward serving manufacturers."
 Following that ,they present a circuit for *experimenters*,*hobbyists*.
It's not full DAA suitable for *production* designs,but good for
*prototyping* DTFM apps.
 It is based on a circuit presented in Encyclopedia of Electronic
Circuits,Volume 5,by Graf and Sheets(Mc.GrawHill,1995;ISBN
0-07-011077-8).They give the specific component values and sources and has
been tested.
 Application Notes page 359 BSII

>
>>If your app dosen't involve connection to phone lines, then all you need
>>to worry about is if the detector will respond properly to your sqawk.
>:)

 Of course I'm connecting to the phone line and all the hardware is easy to
find even at any garage sale (answering machines and phones for about 5
bucks). My worry is not the hardware but the software for the PIC because
each Basic StampII costs $49 or $25 the single PIC 16c57 programmed(ready
for PBasic instructions).

 Hope this give you an answer.

 "The LORD is my rock, my shield."
 " Happy of those who fears The Lord "
                     Humbleness is the clue.
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