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From: mark@tove.UUCP (Mark Weiser)
Newsgroups: net.dcom
Subject: RJ-41S and RJ-45S
Message-ID: <90@tove.UUCP>
Date: Thu, 17-Jan-85 11:35:04 EST
Article-I.D.: tove.90
Posted: Thu Jan 17 11:35:04 1985
Date-Received: Fri, 18-Jan-85 10:23:43 EST
Distribution: net
Organization: U of Maryland, Laboratory for Parallel Computation, C.P., MD
Lines: 53

What can anyone tell me about RJ-42S and RJ-45S telephone connections?
I'll tell you what I know.

I just bought a couple of Anderson Jacobson 4800 baud modems for use
over regular 2-wire telephone lines.  However they arrived with,
instead of the little 4 connector modular plug (RJ-11C), with an
8-wire modular plug into the phone system, which they call an
RJ-41S or RJ-45S (I don't know what the difference is).  They claim
the phone company must come out and install the corresponding 4-wire jack.
Here is what they say about using the RJ-11S:

	"Connecting the modem to the telephone line with an RJ-11C jack
	is not recommended, although it may work under certain conditions.
	An RJ-11C voice jack requires a 4-wire telephone cable, not supplied 
	with the AJ-4048 modem."

Actually not only do they not supply the 4-wire cable, but they don't supply
anyplace on their modem where the 4-wire cable could plug in.

I also think I am going to need to get myself a phoneset with an 8-wire 
connector since the AJ doesn't autodial.  Are these available?

My questions are:
	A. Is it likely to be a big deal or a little deal for the phone
	company to install that 8-wire jack in my house?  Are the 8 wires
	in the wall somewhere or does a major restringing occur?  (I would 
	guess from the descriptions of wires 7 and 8 below that they are
	just a volume control from the phone company built into the box.)
	B. Are there adaptors available to go from 8-wire to 4-wire connectors
	and back?  The quote above implies it is somehow possible.
	C. What is the real difference?  What are the circumstances under
	which RJ-11C will not work but RJ-41S will?

Thanks for any and all help.
By the way, the 8 wires are identified as follows (in the AJ manual):

	1. no connection
	2. no connection
	3. Mode indicator.  Selects voice or data mode depending on state of
	   telset exclusion switch (or other control).
	4. Ring.  One side of telephone line.
	5. Tip.  Other side of telephone line.
	6. Mode Indicator Common.  Ground.
	7. Programming Resister.  Resistor (on data block) used to 
	   control modem transmit level.
	8. Programming resistor common.  Return side of PR signal (7. above).

7 and 8 are identifed as: "Passive or isolated signal", and none of the
rest are, whatever that means.
-- 
Spoken: Mark Weiser 	ARPA:	mark@maryland	Phone: +1-301-454-7817
CSNet:	mark@umcp-cs 	UUCP:	{seismo,allegra}!umcp-cs!mark
USPS: Computer Science Dept., University of Maryland, College Park, MD 20742