• What kind of modem do I need for ISDN?
• Should I use a TA or a Router?
• Can you recommend any brands/models of hardware?
• Where can I find an RJ11 to an RJ45 Jack for my ISDN TA?

To use your ISDN phone line you will need either an ISDN Terminal Adapter
(TA) or an ISDN LAN Router.

ISDN Terminal Adapter
An ISDN TA acts very much like a standard analog modem by connecting to your computer and then plugging into the ISDN phone line. In fact, Windows uses a TA just like a modem; requesting it to go off hook, dial, etc. To use a TA you use standard Dial-Up-Networking in Windows. The TA connects to your computer by either a serial port cable (just like a standard modem) or USB.

ISDN LAN Router
An ISDN LAN Router is very much like a network hub, but it also connects to your ISDN phone line. Your computers will connect to the router via an Ethernet cable and are configured to route all requests for internet activity to the router. When your computer requests a web page from the router the router will dial your ISP and connect to the internet. The router is configured with all the information it needs to know to call your ISP (user name, password, phone number, etc).

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by brawney

You should first make sure you understand the advantages and disadvantages of each type of hardware.

Pros and Cons of a TA

•If your TA connects to your computer via the serial port the speed of your connection will be limited to the speed of the serial port. Most serial ports run at a max speed of 115kbps. Your ISDN line can potentially run at a max speed of 128kbps. You may be wasting a small amount of speed because the ISDN line and TA can run faster than the serial port.
•You will get better performance by using a USB connection to your TA.
•A TA is great for connecting one computer to the ISDN line and internet. If you want to share your internet connection with more than one computer you will need to use Windows Internet Connection Sharing.
•All configuration is typically done in Windows dial-up=networking.

Pros and Cons of a Router

•A router is operating system independent. Any computer on your network can connect to the router via the Ethernet connection regardless of its OS.
•You can easily share the internet connection between multiple computers in your home without using Windows Internet Connection Sharing and requiring the gateway computer to remain turned on.
•You will usually realize the fastest speed when using a router because you are not limited by a serial port connection to the computer.
•The router configuration is done in the router itself, either via special software, Telnet, or a browser interface to the router configuration screens.

OK, so which one should I use?
Most folks in the forum will recommend a router. They are easy to setup and it is very easy to share the internet connection with several computers in your home. But a TA will work just fine too, so if you are more comfortable with a "modem like" device connected directly to your computer or have found a great deal on a TA then its fine to use a TA. Just make sure you know the difference between the two types of hardware before making your decision.

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by brawney
last modified: 2002-09-10 18:50:34

In the US you want to make sure that the hardware you get has a "U" interface. This is different than the S/T interface used in Europe. eBay is a very popular place to get good quality used hardware at very cheap prices. For example, a 3COM 3C892A LAN Router sells for about $300 new but you can easily pick one up on eBay for under $100 (many times under $50). Just make sure you get a "U" interface for use in the US. If the auction doesn't specify the model of the unit then ask the seller before bidding.

Many people in the forums have recommended the following hardware:

•NETGEAR ISDN Products - RH348 and RT338 routers

•CISCO 800 Series Routers - 802 and 804 are very popular models for use in the US

•3COM OfficeConnect 3C892A LAN Router (they call it a LAN Modem)

•US Robotics ISDN Pro Terminal Adapter (3CP3468A)

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by brawney
last modified: 2002-09-10 18:49:11

While it might be difficult to find an RJ11 to RJ45 cable, you don't need to find it. A regular RJ11 to RJ11 will work.

RJ11 to RJ11 is a regular phone cable. They're cheap and super easy to find. It will fit into the RJ45 jack on your modem. Since ISDN only uses the center 2 pins on an RJ45, and an RJ11 has 2 pins in the center ones, you don't need the extras.

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by eriksvend edited by redxii
last modified: 2003-06-26 21:41:24