sbhattac@sales.GBA.NYU.EDU (Shankar Bhattacharyya) (03/19/91)
I need some help with communications over leased lines. There is a four wire leased line, with a terminal at one end, and a 386 machine running SCO Xenix (3.2) at the other. At each end there is an AMT Star modem, which is claimed to be compatible with a Hayes 2400. The line will be used exclusively for the incoming connection. Communications, of course, don't work, because the modems do not support four-wire lines directly. They can be made to work with two wire leased lines, according to the manufacturer. The connections between terminal and modem at one end, and computer and modem at the other are apparently OK. One can connect to the modem using cu, addressing it as a direct line, so it is possible to set things in non-volatile memory, and then get out. I would appreciate pointers to information on getting this to work. I know almost nothing about leased lines. I gather they need something called a hybrid at each end, and these should be in place today. There are no manuals on anything except the modems, and those have not yet enabled me to figure out what I need to do. Neither the vendor nor the owner found it useful to keep the Xenix manuals, but I have access to standard Unix manuals. I believe I can sort out the Unix issues anyway. Once the leased line issues are straightened out, is there some way to ensure that the modem at the computer end can be set to establish the link without hassles, given complete Unix incompetence at their site? Is the leased line issue completely separate from any Unix matters? How do I go about making this work? I would appreciate any help I can get. Thanks for any advice, including pointers to documentation. - Shankar ---------------------------------------------------------------------- Shankar Bhattacharyya, Information Systems, New York University sbhattac@sales.stern.nyu.edu ----------------------------------------------------------------------
tronix@polari.UUCP (David Daniel) (03/20/91)
You want to make sure of a couple of things (at least) regarding the modems:
1. Make sure they're both set for Leased Line operation (register S27).
2. If you're using cu then you'd want the calling modem set appropriately.
On my PB 2400 Plus S27 bit 0,1 allows these options:
0 async.
1 sync. mode 1: async. control of call placement.
2 sync mode 2: stored number dial controlled by DTR.
3 sync. mode 3: manual dial thru DTR control of data/talk switch (requires
telephone handset).
bit 2 is 0 for dialup line, 1 for leased.
bit 3 is not used.
bit 4 is source for sync. transmit clock: 0 modem (EIA pin 15). 1 data terminal
(EIA pin 24).
bit 5 is reserved
bit 6 0 for CCITT 1 Bell 212A
bit 7 reserved
I think a standard leased line is supposed to be 4 wires. Either way, the
wiring of the jacks is the crucial part.
--
David Daniel (The man with no disclaimer) tronix@polari.UUCP
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