The system is run from a single rack unit box called the X1 Encoder, which is actually based upon a personal computer server and digital audio hardware from Lynx Studio Technologies (LST). Control is entirely via software, via gigabit Ethernet, USB, serial port, and SVGA video monitor. All processing is handled internally by a Pentium 4 running Windows XP.
FMeXtra is fully compatible with HD Radio hybrid mode, which uses additional radio spectrum beyond the ±100 kHz signal. It is not compatible with HD Radio in all-digital mode; however this is not expected to be used for a very long time, given that there are already billions of analog FM radios already in use. It is also not compatible with all existing subcarriers. Thus, a public radio station might have to remove its radio reading service for the blind, and replace it (and its dependent listeners' receivers) with a digital one. This would take up much less bandwidth, particularly since voice can be highly compressed; however, the changeover could be somewhat disruptive. The signal is partitioned so that RBDS, stereo, or other existing subcarriers can be protected, at the expense of bandwidth. But if you transmit in mono mode only, you have no RDS protection for stations in Europe.
The codecs used are AAC and aacPlus v1 and v2 and sample rates of 8 kHz (telephone quality) to 96 kHz (surround sound quality). The other codecs used are AMR-WB+ that can create more multiple audio programs as well as limited multimedia can also be broadcast, as with HD Radio and DAB. The available broadcasting bandwidth for digital audio varies from 40 kbit/s while sharing the space with existing analog signals, or 156 kbit/s if all analog signals (except the base monophonic signal) are dropped. (For comparison, iBiquity's Hybrid Digital/analog system offers 100-150 kbit/s in shared mode, and 300 kbit/s in pure digital mode.)
The system works very well for high power transmitters, but does not work for low power FM transmitters if the area covered does not have good stereo coverage. The coverage is similar to FM Stereo, and therefore high ERP is required in larger urban areas, as with normal FM transmissions.