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Re: Mobile HAM AID box



I have experimented quite a bit with CallerID stuff.  I don't see too much
problem generating the appropriate signalling to cause the unit to decode.
The only possible downside, is that you will be constrained to the SMDF and
MMDF data formats which govern the CallerID protocol.

SMDF delivers just a timestamp and calling number information.  The display
unit will decode and display the 10 digit phone number but then display
something like "UNKWOWN NAME", "OUT OF AREA" or "ANONYMOUS" for the calling
name field.

MMDF delivers both the calling number and calling name information if it
is available.  The calling number is again constrained to a 10-digit
phone number like thing...  but the calling name field can be fairly
generic.

The data is transmitted as 1200 baud, async with some start of frame
and checksum information.

The Motorola MC14LC5447 datasheet sheds alot of light on how it works.

http://mot-sps.com/products/telecommunications/miscellaneous/caller_id/mc14lc5447.html#documentation

Chris

Bob Bruninga wrote:
> 
> APRS ID BOX (AID)
> At DCC I presented the idea of using the ubiquitous Caller ID boxes
> as a Ham Radio universal mobile 4 line message delivery device.  
> These devices are down to $12 on sale and $2 surplus.  Not only can 
> they display real-time messages, but also have a 50 to 100 message 
> memory.  I call this an AID box (APRS ID BOX).
> 
> The application is the dashboard of every mobile ham radio vehicle.
> NO OTHER HARDWARE REQUIRED.  Just connect to your speaker.  Imagine 
> the applications:  Meeting announcements, traffic/wx advisories
> bulletins, Emergency calls, etc.
> 
> The beauty of it is that they use 1200 baud standard ASCII text  and
> the same Bell202 tones as Packet radio.  All we need to do is 
> transmit the right tones!  Any TNC with "ASCII" RTTY mode can do this.
> THus it should be trivial to implement a universal LOW COST amateur
> text distribution system almost overnight!
> 
> Before DCC I began experimenting.  I could easily use a BELL202
> modem to receive caller ID from my phone line.  But for transmitting
> to an AID box, it appears that the ID box will not receive and 
> decode the text unless the ASCII tones arrive at a specific time 
> after the first ring signal.  Reverse engineering the circuit reveals 
> the ring rectifier does feed a pin on the PIC chip which will need to 
> be spoofed; probably by the opening of the squelch.
> 
> The concept is to have a modem at each voice repeater site to 
> send the tones.  It listens for special messages on a command
> channel (or the APRS channel) and translates them to the AID
> format.  The ideal engine to program this cross translator 
> is the TAPR Pic-E which alreaady has the Bell202 modem on board.
> 
> Thus, not only APRS stations, but also ANY voice radio user can now
> be efficiently informed via error-free text messages for under $5
> per vehicle!
> 
> Experimenters go for it!
> 
> de WB4APR, Bob
> 
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> 


-- 
Chris Elmquist
chrise@n0jcf.com
----
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