MAT-TRANS is short for Matter-Transmitter, a teleporter used as a plot device in James Axler's Deathlands and Outlanders series.
The device is typically a six-sided room with walls, floor and ceiling made of "armaglass", a likely fictitious type of glass which is very difficult to break or shatter. Each one is usually a different color from the others. There is a single door in this room made of vanadium steel. The entire chamber is difficult to destroy or damage due to the high level of armoring of the walls and door, but accidents have been known to happen, and the characters, especially in Deathlands, express a fear of coming out of a transporter that is a mile underwater, or buried under a thousand tons of rock. They've come very close in the past.
The chamber is activated by computer systems from outside, but if there is nobody outside of the mat-trans chamber who knows how to operate those devices (as is typically the case in Deathlands,) then it can be triggered simply by closing the door. The second option is by far the less preferable, especially because it sends the users to a completely random chamber. There is a Last Destination button, which if used, will send the users right back where they came from, but there is a time limit on how long before this button is rendered useless until the next jump.
The method of how this machine works is unclear, but the basic gist of its operation is this: it breaks the travelers up into digital copies of themselves and transmits them through a quantum tunnel to the next mat-trans, where they are reassembled. As a general rule, it has greatly adverse effects on the users, whose side effects have been known to include nosebleeds, headaches, vomiting, and more. In Deathlands, the character Mildred Wyeth has been known to attempt to concoct what she dubs "jump juice", using medicines, herbs and alcohols, but each batch is slightly different, and some work better than others. Some have been known to clear up symptoms in mere minutes, others have been known to make them worse.
The Outlanders series by Mark Ellis (writing as James Axler) has provided a fairly extensive backstory for the mat-trans or gateway units. The inaugural novel in the series Exile to Hell (1997) contains a complete description of the mat-trans operation, as well as the formal name for the device: Quantum Interphase Mat-Trans Inducer.
The machines were developed in the late twentieth century by Mohandus Lakesh Singh, who was the first human being to have traveled by the system.
Outlanders also established that "jump sickness" afflicting the Deathlands characters was because specific destination codes were not entered into the gateway's targeting computer and therefore the matter stream modulations between the two gateways are not synchronized. As explained by Donald Bry in the Outlanders novel, Destiny Run(1997): "If the modulations are synchronized, you slide along the quantum path to your destination. When they aren't synchronized, one more or less slams into one's destination."
The mat-trans travelers in Outlanders rarely suffer from debilitating side-effects as described in Deathlands.
Outlanders also introduced a smaller, more efficient and portable device spun off from Lakesh's mat-trans units, called an interphaser.