Network B customer the call must traverse two separate Radio Access Networks, two core networks and an interlinking Gateway Mobile Switching Centre (GMSC) which performs the physical interconnecting between the two providers. IP calls With end-to-end QoS managed and assured rate connections, latency can be reduced to analogue PSTN/POTS levels. On a stable connection with sufficient bandwidth and minimal latency, VoIP systems typically have a minimum of 20 ms inherent latency. Under less ideal network conditions a 150 ms maximum latency is sought for general consumer use. Latency is a larger consideration when an echo is present and systems must perform echo suppression and cancellation. Computer audio Latency can be a particular problem in audio platforms on computers. Supported interface optimizations reduce the delay down to times that are too short for the human ear to detect. By reducing buffer sizes, latency can be reduced. A popular optimization solution is Steinberg's ASIO, which bypasses the audio platform and connects audio signals directly to the sound card's hardware. Many professional and semi-professional audio applications utilize the ASIO driver, allowing users to work with audio in real time. Pro Tools HD offers a low latency system similar to ASIO. Pro Tools 10 and 11 are also compatible with ASIO interface drivers. The Linux realtime kernel is a modified kernel, that alters the standard timer frequency the Linux kernel uses and gives all processes or threads the ability to have realtime priority. This means that a time-critical process like an audio stream can get priority over another, less-critical process like network activity. This is also configurable per user (for example, the processes of user "tux" could have priority over processes of user "nobody" or over the processes of several system daemons). Digital television audio Many modern digital television receivers, set-top boxes and AV receivers use sophisticated audio processing, which can create a delay between the time when the audio signal is received and the time when it is heard on the speakers. Since TVs also introduce delays in processing the video signal this can result in the two signals being sufficiently synchronized to be unnoticeable by the viewer. However, if the difference between the audio and video delay is significant, the effect can be disconcerting. Some systems have a lip sync setting that allows the audio lag to be adjusted to synchronize with the video, and others may have advanced settings where some