Critical Wireless Communications and
Weather Information Systems

VoIP Communications Gateway

ED-137 Gateway

When it comes to digital voice communications the standard for Voice over IP (VoIP) for aeronautical communications does not use the common compression algorithms such as G.711, G.722, G.729 etc. neither does it use the radio over IP modes in the two-way radio industry such as DMR, IDAS, MotoTRBO, Nexedge, P25 or Tetra.

Aeronautical communications or “Voice ATM” communications include all voice applications used for the purposes of Air Traffic Management (air-ground communications, co-ordination and transfer, emergency, Search and Rescue, flow management, capacity planning), ATM voice covers intra- and inter- center (all types of ATSUs: ACC, APP, TWR, MIL, NMOC) communications and also ensures the connectivity between the centers and the ground radio based stations on the ground leg of the Air-Ground communications between controllers and pilots. Thus it is a very unique and “critical” type of communications and as such it has to operate according to very high standards of reliability, robustness and interoperability.

The Working Group EUROCAE WG-67, with cooperation from EUROCONTROL, European industry, and ANSPs, developed the first VoIP in ATM standard. The standard was issued in February 2009 as a set of documents (ED136-138) defining the operational voice concept, the interoperability solutions and the network- associated requirements. A new version of the standard (ED137B) was released in February 2012 after a review which included integration of requirements from the U.S. Federal Aviation Administration (FAA).

Currently ED-137B and the newer ED-137C are the only VoIP standards recommended for use in ATM networks.

Morcom offers a unique and powerful gateway used to adapt traditional analog communications to the new ED-137 standard. In addition, the CRU995 Gateway can be used to extend the useful life of both legacy VCS systems and legacy radios. The CRU995 module was designed as an efficient, less expensive remote IP/4 wire E&M interface, for a maximum of 4 transmitters, receivers and/or transceivers. Thus one CRU995 will allow you to control and use up to 4 radios over an IP line.

Click HERE to download the brochure.


  • Connect an analog VCS switch to a group of analog radios over an IP connection
  • Connect an analog VCS switch to one or more digital radios
  • Connect to a SIP phone line
  • Connect a VCS over distance to a group of radios over one standard E&M line

The diagrams that follow illustrate the multiple ways that the CRU995 can be used.

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