Narrow Band Emergency Messaging System is a suite of programs that communicates using various "sound card" modes. It requires a transceiver and your computer's sound card, and perhaps an interface such as Signalink or Rigblaster. You don't need a TNC.
NBEMS is widely used by amateur groups engaged in emergency communications. All programs can be downloaded from http://www.w1hkj.com/ or Source Forge. Versions can be run on Windows, Linux, and Mac.
This page is not intended to answer every question or solve every problem. That's what Elmers, practice, drills, and nets are for. But maybe this will help you get started.
The heart of NBEMS is the app "fldigi" which is a fast, light, digital modem. Fldigi generates the signals in the mode being used and sends them to your sound card, and decodes the incoming signals. An app called flmsg links to fldigi to handle messages.
As of 2/8/18, we are using fldigi ver 4.0.15 and flmsg ver. 4.0.5
Fldigi offers multiple modes - from MT63 to PSK31 to . . . get this . . . CW!
For VHF/UHF emcomm, and on one of our digital nets, we will use MT63-2000L, which is fast enough for our purposes and somewhat resistant to noise. The author of this page was able to get a message through using MT63-2000L when an analog FM signal was unreadable.
For HF Emcomm work using fldigi, the mode "Olivia" is preferred. Olivia enables you to do what I used to think was impossible - make contacts below the noise floor.
Two files are available below for downloading - an "Introduction to NBEMS" and "Advanced NBEMS" They can help you set things up once you've downloaded fldigi and flmsg.
Upon installation of the latest version of flmsg, the program uploaded the latest versions of templates and message forms, which includes some ICS forms (205, 213, 309, etc.), ARRL radiogram, Red Cross forms, MARS forms, and more.
DuPage ARES conducts a net using MT63-2000L on the third Tuesday of alternate months, switching back and forth with EasyPal. Kane Co. ARES has regular nets using fldigi. All amateurs are welcome to join these nets to test their digital messaging setup and skills.