I am struggling to connect any form of modem through my ProLogix switch. We moved to a new building about 2 years ago with a set of analogue modems that used to connect direct to Telco copper lines. These are now connected into an analogue card on the switch and the switch has a PRI line to the Telco (British Telecom). The connections we were achieving were much worse than previously on the direct lines.
The problems are several, firstly the modems take many attempts to connect (10 tries is not uncommon), secondly we get lots of data errors, causing many re-transmissions (the lines are running PPP). Consequently, data rates are very poor (1kb/s is about the maximum).
Finally, the lines regularly drop out. Keeping the connection open for more than 15 minutes is sometimes impossible.
To try to solve the problem I have replaced the analogue modems with Eicon digital modem cards (4BRI Diva Server card) connected to a BRI card in the switch.
To my utter amazement, this was no different. Exactly the same problems (poor connection, low connection speeds and low data rates) occur with the digital modems as with the analogue modems.
I would welcome any suggestions of what to try. I have tried connecting to the digital modems as an internal call and always get very good connection (upwards of 52k connection, data transfer rates >4kb/s). I can only think that the problem is with the setup of the PRI line, or with BT. I have heard mention of "bit slip", but I don't really know what this is or what I can do about it.
Tim Wright
The problems are several, firstly the modems take many attempts to connect (10 tries is not uncommon), secondly we get lots of data errors, causing many re-transmissions (the lines are running PPP). Consequently, data rates are very poor (1kb/s is about the maximum).
Finally, the lines regularly drop out. Keeping the connection open for more than 15 minutes is sometimes impossible.
To try to solve the problem I have replaced the analogue modems with Eicon digital modem cards (4BRI Diva Server card) connected to a BRI card in the switch.
To my utter amazement, this was no different. Exactly the same problems (poor connection, low connection speeds and low data rates) occur with the digital modems as with the analogue modems.
I would welcome any suggestions of what to try. I have tried connecting to the digital modems as an internal call and always get very good connection (upwards of 52k connection, data transfer rates >4kb/s). I can only think that the problem is with the setup of the PRI line, or with BT. I have heard mention of "bit slip", but I don't really know what this is or what I can do about it.
Tim Wright
