From: utzoo!decvax!duke!harpo!utah-cs!slinac!derek
Newsgroups: net.dcom
Title: Which modem should I choose?
Article-I.D.: slinac.119
Posted: Fri Aug 20 01:52:29 1982
Received: Sat Aug 21 02:12:47 1982


Thank you so much to all who replied to my query.  Several questions
have come up in response to all of the replies which I received.  I
will also summarize the replies received so far.

I am trying to select a 300/1200 baud, auto-answer (with speed recog-
nition), auto-dial modem for dialing Usenet with uucp, (unattended),
and dialing other computers (with cu).  The unit should also be able
to act as a dial-in.

Q:	How important is tone dialing?  It has been said that pulse
	dialing will not pass through the exchanges to remote PABX's.

Q:	Is a dial tone detection important when dialing out on centrex
	or is a time delay adequate?

Q:	What drivers are available for the different types of modems?

If your system is equipped with an auto dialer, what is it?  Does it
dial Usenet automatically?  I will summarized this list and post results.

Summary of responses:


The Racal-Vadic 3451PA and the Ventel 212+ seem to be the prime
contenders based on the responses (most were about these units)
and the price.  The 3451 is pulse only whereas the 212+ is also
touch tone (however, someone indicated that it's tone dialing is
not reliable.)  Neither has a dial tone detection circuit.  Both
run 300 baud (103) and 1200 baud (212) but the 3451 also has a
3400 protocol.  The 3400 is more reliable, allowing RV to develop
a 1200 baud acoustic coupler.  Both units do auto bauding on answer
but the 3451 requires a second rs232 line to indicate the speed.
The 212+ rasises carrier when powered on (allowing Unix to open
the line). This means a user MUST log out at the end of the session
or Unix will never know about it.  The 3451 requires an operating
system hack to allow the user to open the line before carrier is
raised.

Ignore the Novation line of modems.  Their 1200 baud is half duplex
using 202 (not 212) protocol.  This is a dying beast.

The Anderson Jacabson 1259 and the Datatec 212a
are very similiar in operation to the Racal Vadic 3451 but neither
has the 3400 protocol.

Other units which I have no information on and probably should be
looked at are OZ225 (expensive but LOTS of features), Penril,
Hayes 1200, and Cermetek 212a.

It is possible to purchase your auto-dialer and modem seperately.
DEC offers a DF03 pulse dialer with a manual switchable speed on
the modem.  Racal Vadic has a VA811 auto-dialer and 831 modem.

Well, that is where I stand.  Which would you choose?  I do not
know much more that what is displayed here.  Some offer the
capability to store frequently dialed numbers but that does not
apply to my situation.

If any information here is incorrect, please post an item to
net.dcom so everyone will see it.