Frequently Asked MIL-120A, MIL-140T, MIL-160T Media Converter Product Questions

1. If I use a MIL-120A to connect a node to a UTP hub, how long can the cables be?
2. What is the function of the DIP Switches on a MIL-120A?
3. I am connecting a MIL-120A into my Sun workstation via UTP, and it won't work. What is wrong?
4. What are the functions of the Link Sentry Switches on the 140T/160T?
5. What is the function of the HUB/MAU and now MMX/MDX switch on the 140T/160T?

Answers:

• Maximum lengths as defined by IEEE 802.3 are 185 meters for thin-net and 100 meters for UTP. A maximum of 10 units MIL-120A is recommended, and longer cable distances will limit the total number of MIL-120A.

• They select internal termination for thin-net.
  1. If you use a T connector with a 50 ohm terminator attached to the MIL-120A then both switches should be UP (OFF).
  2. If you want to run the cable directly into the MIL-120A without a T connector, then put either switch DOWN (NOTE: If this is a last device in the Net otherwise both switches are UP).
  3. If you use a T connector that attached to the MIL-120A just to expand to two different nodes then both switches should be UP (OFF).
  4. If you run short distances of 2 meters or less, then try both switches down for 25 ohms of termination. If your segment is around 1-2 meters and you are having problems, then use a longer cable with 50 ohms termination or a shorter cable with 25 ohms of termination.

• Most likely, the problem is that you are using a straight- thru cable. You must use a "swap" or "cross-over" cable, which swaps the transmit and receive pairs. When connecting two devices that transmit and receive on the same pins, then you need to wire that transmit pair of one into the receive pair of the other. A swap cable (1-3, 2-6, 3-1, 6-2) will accomplish this.

• The switches provide extra features when you are using them in a redundant or fault tolerant system by dropping the connection on both sides of the unit if one link happens to go down.

• This switch eliminates the need for using a swap or crossover cable when connecting it to your network. Please try both positions if you are unsure. The link light will light when it is in the correct position.