Re: Capability terminology

[Graham Klyne <GK@xxxxxxxxxxxxxx>]

At 11:49 13/11/98 -0800, Dan Wing wrote:
>On Fri, 13 Nov 1998, Graham Klyne wrote:
>
>> I do not see the sender disclosing any of its capabilities to the recipient
>> in G3 fax.  
>
>Doesn't the DIS go one directiona and the DCS the other direction
>(sender->recipient and recipient->sender)?  I'm not a fax person and my
>copy of T.30 is at home (of course) and I'm at work.  I've certainly
>been wrong before and am likely to be wrong again.

I, too, could be wrong.  But my reading is this:

For a normal fax transmission, called terminal sends DIS to indicate
capabilities, and the caller sends DCS to indicate actual parameters
relating to the image sent (as opposed to capabilities).

When (and only when) the calling terminal is polling for a message, it
sends DTC to indicate its capabilities and the called terminal sends DCS to
indicate specific image parameters.

See T.30 section 5.1 for sequences, and Table 2/T.30 bits 16, 17-18, 44,
49, 76-79 for indication of difference between DIS/DTC bits and DCS bits.

>Your original definition is fine, but I'd just like an additional sentence
>or embedded phrase which clarifies that an "exchange" it isn't necessarily
>a bi-directional exchange (per the dictionary definition of the word
>"exchange").

That's fine -- and matches my intent.

#g