APCO-16

In telecommunications, APCO-16, (sometimes APCO Project 16 or Project 16) is a US standard for the characteristics and capabilities of public safety trunked radio systems.

The standard development effort was started in the 1970s by the APCO, a trade association of mostly police and fire service providers. The program was funded by the Law Enforcement Assistance Administration (LEAA), a part of the US Department of Justice.

APCO-16 describes such characteristics and capabilities as:

With the Federal Communications Commission's pending release of the first 800 MHz band licenses, the LEAA funded a project to develop required capabilities and standards needed in trunked public safety two-way radio systems. The report defined proposed methods for frequency reuse, coordination, and interference reduction. The standards also gained acceptance in businesses such as Specialized Mobile Radio, utility communications systems, and refineries.

The study concluded that those frequencies would be suitable for Public Safety mobile radio uses. The study recognized that certain technical problems like "picket fencing", foliage interference and abrupt signal fall out posed some minor problems, also addressed concerns about health effects from 800 MHz transmitters but did not reveal definitive findings. The availability of the significant additional spectrum and the long term possibility of the eventual collocation of nearly all Public Safety communications into one segment of the spectrum far outweighed these problems.

While the program succeeded in creating basic performance standards and feature sets, it failed to create a signaling standard. The result: three companies built APCO Project 16 compliant systems but radios from each manufacturer were incompatible with one another. In California, for example, University of California, Riverside bought a Motorola system and the County of Riverside purchased a General Electric. In order to communicate, some patch or other custom-built link would have to be installed. Intercommunication was possible but not seamless.

...
Wikipedia