An interesting item appeared in the February issue of Mission Critical magazine and relates to previous Tech Topics. In Tech Topic #2 , it was suggested that interoperability among disparate radio networks could be attained at the networking level by using Internet Protocol-based bridging or gateways for each individual radio network. Alternatively, in Tech Topic #3,  it was shown that interoperability could be attained at the physical level via bridging or gateways that provide for the physical level transformation of transmitted signals between disparate networks.
The Department of Homeland Security recently announced the establishment of a standard for interoperable gateways. This standard for Voice over Internet Protocol (VoIP) based bridges and gateways will allow the proprietary systems of multiple vendors to interoperate via a common interface standard. Testing of the standard is beginning with a goal of having a voice only standard published by the summer of 2008.