Re: How to terminate a twinax termination for a 3487 dumb terminal

Wayne McAlpine wrote:

As I recall the 3487 is self-terminating. You don't need to connect anything to the second cable.

What you have on most Twinax terminals is a device called an auto-terminator. On IBM Twinax terminals from the InfoWindow series on, this is normally a Y-fitting, with 2 female Twinax pigtails growing out of a D-connector that plugs into the back of the terminal (the whole assembly is usually beige); for products of Andrew and Affirmative, this is normally a T-fitting, with two female Twinax connectors and a single D-connector pigtail in a single T-shaped housing, with the whole assembly usually black.

As I recall, 3180s have a little black module with 2 female Twinax connectors, that bolts into a slot on the back of the screen housing; that may be an early form of auto-terminator.

In my own experience, Twinax is quite forgiving of improper termination. In my office, I have two terminals, one with 4 lines coming in through a mechanical switchbox, and the other with 2 lines coming in through another mechanical switchbox. Two of the lines going to the 4-way switchbox are tapped with T-fittings to feed the 2-way switchbox. There have been rare occasions when connections crashed because of impedance and/or reflection issues, but they've been so rare, I can't remember the last time it happened (more often, it's because of poor contact in the switchbox)