whh@jhunix.UUCP (William H. Huggins) (06/21/86)
Using a Racal-Vadic 3451 Modem with a UNIX-PC. A remote terminal using a Racal-Vadic 3451 modem could communicate at 1200 baud with a UNIX-PC running System Software Version 2. But with the upgrade to Version 3, the Racal-Vadic 3451 may not be able to login through the built-in modem of the UNIX-PC because of the time-out before the 212 protocol can be set up by the 3451 modem unless special care is taken to assist that modem in finding the appropriate mode. Because many 3451 modems are in use, this may be a frustrating difficulty for users who attempt a remote login to a UNIX-PC. I would like to describe a way of avoiding this difficulty. The UNIX-PC built-in modem operates in either 212 Mode or 103 Mode. The Racal-Vadic 3451 operates in three modes: 3400, 212, or 103. On initial connection, it assumes 3400 mode, and only if this fails after several seconds does it change to the 212 mode and repeat its effort to establish communications, which takes several seconds more. Unfortunately, because of the time lost in first trying the 3400 mode, there is not sufficient time left before time-out (apparently about 10 seconds) to complete the 212 synchronization, the UNIX-PC disconnects, and login is aborted. When the 3451 is manually dialed, it is possible to speed up this mode search by throwing the VO-DA switch to DA position *immediately* after the last digit of the phone number is dialed rather than waiting for the UNIX-PC modem to answer. If this is done, the 212-mode synchronization can be completed before the UNIX-PC aborts, and communication at 1200 baud can achieved as intended. The AT&T folk claim that there should be no difference between the earlier Version 2 phone manager and Version 3 but my experience reveals that there is. By eliminating the time lost between the last digit dialed and the activation of the DA switch on the 3451, communication can be established with a UNIX-PC Version 3. I thank John Corbin (AT&T HOTLINE 800-222-9333) and Dave Lum (Racal-Vadic 301-459-7430) for finding this solution to the problem. -- W.H. Huggins
dpw@rayssd.UUCP (Darryl P. Wagoner) (06/27/86)
Thanks for shedding some light on that problem. > > The AT&T folk claim that there should be no difference between > the earlier Version 2 phone manager and Version 3 but my > experience reveals that there is. The Version 3 software is much faster than Version 2. Which may account for the differents. I have the same problem but it not so simple to solve because our vax autodialer is a Racal-Vadic 3451. Hence when uucp uses the Racal-Vadic it can not change the VO to DA switch. Sometime when uucico runs it gets hung. It only uses about 2 or 3 seconds of cpu time. It leaves the lock files and doesn't reset the modem. Has anyone else had this problem. -- Darryl Wagoner Raytheon Co.; Portsmouth RI; (401)-847-8000 x4089 best path {allegra|gatech|mirror|raybed2} ---------\ next best {linus|ihnp4|pyrbos} ---------------------->!rayssd!dpw if all else fails {brunix|cci632} -------------------------/