Williams AV FM 557-12 Large-Area Dual FM/Wi-Fi Assist Listen Syst:12 FM R37 R:FM T55 T/4-PPA R37N/12-Ear 022The FM Plus 557 assisted listening system now with integrated Wi Fi has replaced the existing 457 systems for public venues. The FM 557 Plus offers both FM and Wi Fi transmission from the same box for nearly the same cost as traditional FM systems. This system features the cutting edge PPA TT55 transmitter (replacing the T45 FM transmitter) with multiple digital audio input options and an OLED display with easy to manage navigation, and network