The FM+ PRO intercom system is a turnkey interpretation and assistive listening device that combines FM and Wi-Fi technology in one platform. Featuring 24 PPA R38 receivers and the FM+ C D transmitter with Dante, this system delivers exceptional audio quality, seamless integration, and compliance with ADA hearing accessibility standards.
Ideal for houses of worship, classrooms, government buildings, and performance venues, the FM+ PRO System enables users to listen via receivers or mobile devices for complete flexibility and accessibility.
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The Williams AV FM+ PRO Intercom System merges the reliability of FM with the flexibility of Wi-Fi audio streaming. Built on a DSP platform for exceptional sound performance, it delivers crisp, intelligible communication for live events, training, and presentations.
The FM+ C D transmitter includes Dante audio-over-IP integration, allowing seamless connection to modern AV networks. Users can tune in using professional receivers or personal mobile devices via the WaveCAST app, ensuring accessibility across all communication channels.
With an OLED display, multiple input options, and DSP presets optimized for speech, music, and hearing assistance, this intercom system provides unmatched clarity and adaptability for any professional environment.
The FM+ PRO Intercom System (FM 558-24 PRO D) is a turnkey solution built for professional installations, offering long-range coverage, secure digital transmission, and intuitive operation.
Included in this system:
(1) FM+ C D transmitter with Dante audio-over-IP integration
(24) PPA R38 multi-channel FM receivers with OLED screens
(24) EAR 022 surround earphones
(6) NKL 001 neckloops for hearing aid compatibility
(2) CHG 3512 12-bay chargers
(24) BAT 026-2 AA NiMH rechargeable batteries
(1) ANT 005 remote coaxial antenna
(1) IDP 008 ADA wall plaque
(1) RPK 005 rack panel kit
(1) Coaxial cable for antenna connection
Performance highlights:
Dual FM and Wi-Fi broadcast capability from a single transmitter
Dante-enabled intercom system for seamless AV network integration
DSP processing for superior audio quality and intelligibility
Up to 1,000 ft (304 m) FM transmission range with the ANT 005 antenna
Compatible with the WaveCAST app for mobile listening (iOS & Android)
Third-party control via Telnet over Ethernet for AV professionals
Preset DSP modes (Voice, Music, Hearing Assist) for optimized performance
Complies with 2010 ADA hearing assistance standards
Expandable intercom system that supports unlimited receivers for larger audiences
Compact 19” rack-mount design for clean, professional installation
The FM+ PRO intercom system is built for organizations that need clear, inclusive, and network-ready communication. Whether used in conferences, auditoriums, or educational campuses, it ensures flawless, real-time audio coverage across both FM and Wi-Fi channels.
Important Notes
NOTE: The FCC requires this device to be used with approved, FCC 15.203 compliant antennas and be professionally installed. Refer to Williams AV’s Antenna Selection Install Guide for compliant antennas for this product.
The FM + C connects to the installation location’s Wi-Fi Network. It does not provide a network on its own. The Wi-Fi network will need to be installed and established before the FM + C can be used.
FM + C (FM T55C) Specifications
Dimensions
8.45″ W x 8.25″ D x 1.72″ H (21.5 cm x 21 cm x 4.4 cm)
Weight
Transmitter: 3.2 lbs (1.45 kg)
Color
Black/Silver with silver legends on the front, white legends on the back
Rack Mount
Standard 19” Rack, one EIA rack space high, 1/2 space wide
Rack Mount Notes
1–2 units can be mounted in a single rack space with optional RPK 005 (single) or RPK 006 (double) Rack Mount Kits
Power Supply
Desktop Style Transformer (TFP 062); Input: 100-240 VAC, 50/60 Hz. IEC Line Cord;
Output: 24 VDC, 750 mA, 18W. 2.5mm ID center positive barrel connector
Power ON Indicator
Push On/Push Off latching power button, backlit green indicates power ON; backlight off indicates power OFF;
fading from bright to dark indicates Sleep Mode.
Temperature Range
Operating: +32° F to +122° F (0° C to 50° C);
Storage: -4° F to +158° F (-20° C to 70° C)
User Interface
3.12” High Resolution OLED display with selections via buttons. Hosted Web page. Remote control and monitoring.
Dante
Only available on FM T55C D
Ethernet
RJ-45 on back of unit supports CAT 5e cable lengths up to 328 feet (100 meters);
10/100 Base-T IEEE 802.3 compliant, unique MAC address
RF Section
Operating Frequencies
72.1–75.9 MHz, 17 wideband channels (selectable)
Frequency Accuracy
± 2 ppm stability, 0–50˚ C
Deviation
± 75 kHz maximum
Pre-Emphasis
75 microsec
RF Field Strength
Does not exceed 80 mV/m at 3 m
Compatible Antennas
ANT 005, ANT 021, ANT 024, or ANT 025
Refer to Williams AV’s Antenna Selection Install Guide for FCC-compliant antennas for this product.
Transmission Range
Up to 1000 ft (304 m) with ANT 005 coaxial antenna mounted on rear chassis connector
RF Outputs
(1x) #10-32 stud connector in center of unit (pcb mounted)
(1x) F-connector on rear chassis
RF Transmit Indicator
1 Green LED On Air Indicator
RF Power
Full, Medium, Low or OFF indicated by menu icon
RF Time Out (Sleep Mode)
30 min duration, 4 hr duration, or Always On selected via menu.
Starts when audio is below -18 dB level with no button pressed for selected duration.
Audio Section
Audio Processor Functions
DSP based; Compression: 1:1, 1.5:1 or 2:1; High-pass and Low-pass Filter Frequency control
Frequency Response
31–16000 Hz, ±3 dB (re: 1 kHz) (“Music” Audio Preset)
Signal-to-Noise Ratio
67 dB (typical) transmitted RF
Total Harmonic Distortion
< 0.25% @ 1 kHz (RF output)
Common Mode Rejection
> 57 dB @ 1 kHz, Mic or Line
Audio Inputs
(1x) Combination 3-pin XLR, 1/4″ (TRS) jack for balanced/unbalanced line level, or mic with selectable phantom power
Audio Input Gain Adjust
In menu, adjustable 0 to -50 dB, in 1 dB steps
Phantom Power
14.4 VDC through 2.2 kOhms resistors to analog combo jack:
Pin 2 and Pin 3 on XLR, or tip and ring on 1/4″ TRS
Audio Level
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Unlike traditional systems, the FM+ PRO intercom system combines FM and Wi-Fi broadcasting from one transmitter. It integrates with Dante networks, offers ADA-compliant assistive listening, and lets audiences connect through receivers or smartphones simultaneously.
Yes. The FM+ C D transmitter includes a Dante interface, allowing seamless routing of digital audio between networked AV components. This simplifies installation and enables professional audio control across large intercom system deployments.
The system delivers up to 1,000 feet (304 meters) of FM transmission when paired with the ANT 005 antenna. Wi-Fi streaming range depends on the venue’s network infrastructure, making it ideal for large auditoriums and multi-room facilities.
Absolutely. Listeners can tune in using the free WaveCAST app on iOS or Android. This feature allows audiences to use their smartphones as receivers while maintaining broadcast quality equal to the physical R38 units.
Yes. The package meets 2010 ADA standards for assistive listening. It includes neckloops, earphones, and signage for accessibility, making it suitable for houses of worship, universities, government spaces, and event venues.
There is no upper limit on the number of FM receivers or WaveCAST listeners. The system supports unlimited users within its coverage range, making it highly scalable for large audiences or multi-language environments.
Yes. AV professionals can manage system settings via Ethernet using Telnet commands or a hosted web interface. This enables remote control of audio gain, channel selection, DSP presets, and transmitter power for efficient facility management.
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