In the "FCC Station Class Codes" list Ive noticed several licenses that list a STANDBY use by the licensee.Some of the Codes are :FB2K-Standby Interconnect,FBK-Standby Base just to mention a few. What & when is Standby used ?
I believe you're correct. Once upon a time, we wanted to have a second repeater on the air as a backup in case our primary repeater went out of service. To get technical, we had two repeaters using the same PL tone on their output and different PL tones on their input. Each radio was programmed with a "primary" and "backup" channel. When the primary repeater went down, you just had to switch channels. If you didn't switch channels, you'd still hear the traffic and eventually figure it out.
Our licensing guru suggested licensing the one site as FB6 and the other as FB6S. In the end, we opted to a) get a second frequency pair for the "backup" site, b) switch to MotoTrbo, and c) use Site Connect to tie the two systems together via microwave. Now the users will not have to switch, and the second site fills in a few dead spots on the west side of the county. They have enough overlap to achieve the redundancy we needed.
Of course, then both sites had to be / are being licensed as FB6.