Studio-to-transmitter link (STL) failure

The STL carries programme audio from the studio to the transmitter site. It may be a radio link, a dedicated line or an internet (IP) link.

• Signs of an STL fault: the studio output is fine and the stream works, but FM / DAB is silent or has switched to backup audio.
• Check the STL encoder or sender at the studio: power, status lights and the network or line connection.
• Many transmitter sites switch to backup audio automatically when the STL fails, so you may hear that rather than silence.
• Engineering will usually need to check the receiving end at the transmitter site. Report the time it started, and what the status lights show.