FM+ C Assistive Listening System


FM+ C is the first transmitter of its kind to offer an FM broadcast and Wi-Fi audio broadcast from a single input source. Whether using the FM+ C for assistive listening, language interpretation, or audio description, this “dual broadcast” technology gives users the option of listening to real-time audio stream on their smartphone or tablet using the free WaveCAST receiver app (iOS and Android) or use an available FM receiver from the venue.

The FM+ C has support for Telnet commands via an Ethernet port enabling AV professionals to control and monitor the FM+ C using third-party room control systems.


The FM+ C integrates professional WaveCAST Wi-Fi audio server technology into a Williams AV FM assistive listening system and integrates with third-party room systems. AV professionals can control third-party room systems with Telnet commands via Ethernet and end users can listen with either an FM receiver or with their own smartphone (via the WaveCAST Receiver App). Along with this flexibility comes exceptional audio quality, as the FM+ C is built on a professional digital audio (DSP) platform.

The FM+ C is designed to support those who want to use their own smartphones and headphones for a more discreet assistive listening experience. Simplicity is also available for those who want a more traditional assistive listening system with a dedicated FM receiver and headset. Venues no longer need to choose between providing FM or Wi-Fi assistive listening systems. FM+ C supports both the new iOS and Android WaveCAST Receiver Apps — in addition to all of the current and legacy Williams Sound FM receivers operating on the 72-76 MHz bandwidth.

Most settings can be changed via the front panel interface, or the hosted web interface. A remote programming guide is available upon request.

The FM+ C uses the WaveCAST app to provide an easy-to-use, intuitive user interface. It is available in iOS or Android. Listeners easily select channel and volume level once their personal device is connected to the Wi-Fi network. The app does not work on FM Broadcasts.

IOS – WaveCAST App

Android – WaveCAST App

*Note: Firmware is model specific. Firmware updates are currently unable to be completed on Mac computers.

System Includes

(1) ANT 025 antenna
(1) TFP 062 power supply
(1) WLC 004 line cord


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.

Audio Inputs (1x) Combination 3-pin XLR, 1/4″ (TRS) jack for balanced or unbalanced line level, or balanced or unbalanced microphone with selectable phantom power. Optional RJ-45 Dante Input (“D” models only).

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
Rack Mount Standard 19” Rack, one EIA rack space high, 1/2 space wide
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 with backlight. Green backlight indicates power ON, backlight off indicates power OFF.
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 1. 3.12” High Resolution OLED display with selections via buttons. 2. Hosted Web page. 3. Telnet commands over ethernet (see our WaveCAST and FM+ Programmers Guide” for available commands and protocol).
Dante (1x) RJ-45 jack. 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. RJ-45 jack used for web page and streaming audio out. An external Router/DHCP Server is required to stream audio to receiving devices.
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, ANT 025, ANT 028, ANT 029, ANT 034

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 F-connector
RF Outputs (1x) #10-32 stud connector in center of unit (pcb mounted)
(1x) F-connector on rear chassis
RF Transmit (RF) Power Indicator 1 OLED On Air Indicator with 4 states indicating power level Off, Low, Medium, and Full Power.
RF Time Out (sleep mode) 30 min. duration, 4 hr. duration, or Always On; selected via web page. When audio drops below -18dB, the selected duration begins, and when it expires the unit stops transmitting and goes into a low-power (“sleep”) mode. Any button press or resumption of audio above -18dB “awakens” the unit and it begins transmitting again.
Audio Section
Audio Inputs (1x) Combination 3-pin XLR, 1/4” (TRS) jack for balanced or unbalanced line level, or balanced or unbalanced microphone with selectable phantom power. Optional RJ-45 Dante Input (“D” models only).
Audio Processor Functions DSP based; Compression: 1:1, 1.5:1 or 2:1; High-pass and Low-pass Filter Frequency control, Music, Voice, and Hearing Assistance Audio Presets
Frequency Response 31-16000 Hz, ±3 dB (re: 1 kHz) (“Music” Audio Preset)
Signal-to-Noise Ratio 64 dB (typical) Transmitted RF @ 1kHz
Total Harmonic Distortion Less than 0.25% @ 1 kHz (RF output)
Common Mode Rejection Greater than 57 dB @ 1 kHz, Mic or Line mode
Audio Input Gain Adjust Adjustable from +24dB to -60 dB, in 1dB steps from front screen or web page
Phantom Power 14.4 VDC applied through 2.2 kOhms resistors to analog combo jack: Pin 2 and Pin 3 on XLR jack, or tip and ring on 1/4″ TRS jack
Audio Level Display Front screen bar graph display, each segment representing 3dB. It ranges from -18 (1 segment lit) to +12dB (10 segments lit). Over-range warning is indicated by ‘OLVD’ and flashing empty bar.
Headphone Output 1/4″ TRS stereo jack, mono signal, 7.8 mW total power with 33 Ω.
Dante Output (1x) RJ-45 jack, only available on FM T55C D
Input Level (Bal or Unbal) (at Audio Input Gain = 0dB)
Nominal (@7th Segment Lit) Overload Warning (Displayed on Screen) Absolute Max. Rating*
-45 dBV (5.6 mV RMS) -20 dBV (100 mV RMS) +20 dBV (10.0 V RMS)
-8.4 dBV (380 mV RMS) +16 dBV (6.5 V RMS) +20 dBV (10.0 V RMS)
Approvals FCC, RoHS3, WEEE, Industry Canada
Warranty 2-year warranty against component failure and manufacturing defects. See the Full Warranty statement on the website for details.* Stresses above these ratings may cause permanent damage or degrade reliability.


2 Years

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Design & Consultant Specs