Williams AV FM 557 PRO – FM+ PRO Assistive Listening System, 4 Receivers

Product Overview

The Williams AV FM 557 PRO is a turnkey assistive listening system with installation accessories, built around the FM+ T55C dual FM and Wi-Fi transmitter and four PPA R37N receivers. It is the right-sized ADA compliance package for conference rooms, courtrooms, training rooms, and smaller worship venues: listeners use the included body-pack FM receivers or stream the audio to their smartphones over the venue Wi-Fi network. The PRO bundle adds a coax antenna, rack panel kit, two-bay chargers, and rechargeable batteries so the system installs without a second accessory order.

Product Description

Installers like this system because the transmitter is genuinely manageable: an OLED display walks through setup at the rack, a hosted web page enables configuration from anywhere on the network, and Telnet over Ethernet ties the unit into third-party control systems for power, status, and level management. Program audio connects through the combination XLR/1/4-inch input, which accepts balanced or unbalanced microphone or line-level sources with selectable phantom power and gain adjustable in 1 dB steps — a clean match for a spare DSP output in a commercial AV system. DSP processing with selectable compression and high-pass/low-pass filtering shapes the feed for speech intelligibility, the property that matters most in assistive listening. The transmitter broadcasts on 17 selectable wideband channels between 72.1 and 75.9 MHz, and the included ANT 005 remote coaxial antenna extends range up to 1,000 feet. Each of the four PPA R37N receivers tunes the full channel set with a recessed seek button, supports channel lock, and ships with an EAR 022 surround earphone; two NKL 001 neckloops serve telecoil hearing aid users. Two BAT KT6 two-bay chargers and rechargeable batteries handle power, and the RPK 005 kit mounts the half-rack transmitter in one EIA rack space. The IDP 008 ADA wall plaque finishes the compliance picture. FCC rules require professional installation with an approved antenna. Need network audio? The FM 557 PRO D variant adds a Dante input; receivers and accessories are in our Williams AV collection.

Key Features

• Dual FM and Wi-Fi Transmitter — The T55C broadcasts to dedicated FM receivers while streaming the same audio over the venue Wi-Fi network for smartphone listeners.
• Install Accessories Included — The ANT 005 coaxial antenna, coax cable, and RPK 005 rack panel kit make this a one-order, rack-ready package.
• Four R37N Receivers with Earphones — Body-pack receivers and EAR 022 surround earphones provide the ADA-required hardware for smaller assembly spaces.
• Rechargeable Battery Kit — Two BAT KT6 two-bay chargers and rechargeable batteries remove disposable battery costs from day-to-day operation.
• Telecoil Neckloops — Two NKL 001 neckloops couple audio magnetically to hearing aids and cochlear implants with telecoils.
• DSP Audio Processing — Selectable compression and filter settings tune the broadcast for maximum speech clarity.
• Telnet and Web Control — Ethernet-based remote management integrates the transmitter with third-party room control systems.
• 17 Wideband Channels — Selectable frequencies from 72.1 to 75.9 MHz allow several systems to coexist in a multi-room facility.
• Unlimited Listener Support — The FM broadcast serves any number of receivers, so the system grows with the venue.

Typical Applications

• Conference room
• Boardroom
• Government space
• House of worship
• Training room
• Commercial meeting space

Technical Specifications

Frequently Asked Questions

What size venue suits the four-receiver package?

Smaller assembly spaces — conference rooms, courtrooms, training rooms, and chapels — where ADA receiver-count guidance calls for a handful of units. The 12- and 24-receiver FM 557 packages cover larger venues, and receivers can be added to this system at any time.

How does the transmitter integrate with a conference room AV system?

Connect a line-level output from the room DSP or mixer to the combination XLR/1/4-inch input, mount the transmitter in the rack with the included RPK 005 kit, and use Telnet over Ethernet if the room control system should manage or monitor it.

Do smartphone listeners need venue Wi-Fi?

Yes. The FM+ joins the installation location's existing Wi-Fi network and does not provide a network of its own, so working venue Wi-Fi must be established before the streaming feature can be used.

Are rechargeable batteries included?

Yes. Two BAT KT6 two-bay charger kits with rechargeable batteries are in the package, supporting roughly 32 hours of receiver runtime per charge; standard AA alkaline cells extend that to about 50 hours.

Is professional installation mandatory?

Yes. The FCC requires this transmitter to be professionally installed with an approved FCC 15.203-compliant antenna. The included ANT 005 is compliant, and the Williams AV Antenna Selection Install Guide lists alternatives.

What warranty applies to the system?

The transmitter carries a two-year parts and labor warranty; the R37N receivers are covered by a Lifetime PLUS limited warranty, excluding earphones, headphones, and batteries.