A/B switching

1. In computing, the act of moving a switch to allow printing, usually, to one of two printers on a single system.
2. In telephony, the ability for a wireless phone to switch from "A" to "B" frequency bands. A-band is the first frequency band assigned for analog cellular service to a non-wireline carrier in each of the US markets as designated by the Federal Communications Commission (FCC). B-band is the first frequency band assigned for analog cellular service to a wireline carrier in each of the US markets as designated by the FCC. Most markets have both "A" and "B" carriers.

Тут никаких особых трудностей нет - ...первый диапазон, частот выделенный аналоговым сотовым службам с беспроводной несущей соответсвующей части американского рынка.