Xref: utzoo comp.unix.aux:572 comp.dcom.modems:3167
Path: utzoo!utgpu!attcan!uunet!fciva!dag
From: dag@fciva.FRANKLIN.COM (Daniel A. Graifer)
Newsgroups: comp.unix.aux,comp.dcom.modems
Subject: Re: Telebit Trailblazer + and A/UX
Message-ID: <444@fciva.FRANKLIN.COM>
Date: 6 Jan 89 15:34:30 GMT
References: <150@radar.UUCP> <590@comdesign.CDI.COM>
Reply-To: dag@fciva.UUCP (Daniel A. Graifer)
Organization: Franklin Capital Investments, Inc. McLean, Va.
Lines: 45

In article <590@comdesign.CDI.COM> pst@comdesign.CDI.COM (Paul Traina) writes:
>From article <150@radar.UUCP>, by root@radar.UUCP (root):
>> Has anyone used a Telebit Trailblazer Plus modem with a Mac II under
>> A/UX? [...]
>I just set one up yesterday.  No flow control (actually, one *could*
>use hardware flow control, since standard modem cables for the mac
>have input-handshake going to pin 5 (cts) on a DB25, but then you
>have no way of detecting carrier).  [...]
>
>All in all the TB+ is wonderful, the Mac leaves something to be desired.
>I'm upset with apple that they do not provide more handshake lines.
>Hardware flow control is the optimal way to deal with a modem, but
>the mac only has one output signal (going to DTR) and one input
>signal (going to CTS for a standard cable, DCD if you wish carrier
>detect).
>
>-- 
>work:	pst@condor.cdi.com	{apple,pyramid,ucsbcsl,uunet}!comdesign!pst

The Prime EXL series ('386 MultiBusII box) has the same problem: only one
handshake line is provided in each direction.  They also use a non-standard
connector: an RJ45-10 (the Mac+, SE, & II use a MicrDIN-8 connector).

The according to the documentation, the early versions also didn't have a
Protective Ground line on their connectors.  The machine as shipped did, 
and the documentation caught up later.  In order to accommodate this, they
had to switch from an 8-pin to a 10-pin jack, but the board design was 
already locked in, with no separate allowance for DSR and DCD, so one pin
of the 10 is unused. 

In both cases, it seems that the manufacturers were looking for a connector 
that was:
	a) Familier to naive users (the MicroDIN-8 resembles an RCA phono
	   plug on a stereo, the RJ45-10 looks like a standard RJ45-8 business
	   telephone modular connector)
	b) A smaller plug to economize on back panal space.
In both cases, it appears that Marketing sense over-rode engineering sense.

	Ah, well....
	Dan

-- 
Daniel A. Graifer			Franklin Capital Investments
uunet!fciva!dag				7900 Westpark Drive, Suite A130
(703)821-3244				McLean, VA  22102