Induction loop system with network control

Ideal Use Cases

The Williams AV DL207 SYS is a medium-area, dual-channel induction loop system designed to extend hearing support to people using T-coil devices. It is suited to spaces such as conference rooms where an installed perimeter loop is required. Published coverage figures apply with both amplifier outputs driven: 30,000 sq. ft. for perimeter loops with a 3:1 aspect ratio and 18,000 sq. ft. for perimeter loops with a 1:1 aspect ratio. The product is designed to meet IEC 60118-4 when the system is correctly designed, installed and commissioned.

Why Choose This Model

The DL207 combines dual loop outputs with flexible source connectivity and network-based control. Its line input accepts balanced or unbalanced signals at -10 dBV, -4 dBu, +4 dBu or +8 dBu, with adjustment from 0 to -96 dB. A three-pin XLR mic/line input supports microphone and line-level sources, balanced or unbalanced operation, and a 24 V phantom supply. A separate high-level input accepts 25 V, 70 V or 100 V signals from distributed audio and paging systems. The line output mirrors the audio supplied to the loop output, helping the unit integrate with a broader installed-audio system.

Installation and Integration

The 1 RU rackmount enclosure measures 19 inches wide by 1.75 inches high by 10 inches deep, with a 17-inch-wide chassis. The DL207 weighs 9.2 lb and uses an internal universal 100-240 VAC, 50/60 Hz, 200-watt power supply with an IEC 320-C14 connection. Variable-speed, temperature-controlled fan cooling supports operation from 0 to 35 degrees C and at 0-90% relative humidity. An RJ-45 Ethernet connection provides 10-100 Mbps networking. Function control and calibration are available through the DigiLoop PC App over Ethernet, with Windows 7 or higher required. Firmware updates are performed through the standard-B USB connection.

Front-panel access is provided through a backlit LCD and a control button/dial. A front 1/4-inch stereo headphone jack can monitor a selected input or output through the menu. The system also provides a two-position terminal block for each loop output, a three-position terminal block for the line output and a dedicated loop fault relay with normally closed, normally open and common contacts.

Performance Highlights

Each output is rated for 9.5 Arms, or 13.4 Apk, with a continuous loop drive voltage of 16.1 Vrms, or 22.8 Vpk. Supported loop resistance ranges from 0.5 to 3.0 ohms DC, while the rated load is 0.5 ohm DC with 135 microhenries of inductance. Frequency response is specified at 45 Hz to 9.0 kHz within plus or minus 2 dB, referenced at 1 kHz. Rated loop total harmonic distortion is less than 1% at rated output current with a 1 kHz sine wave. Audio output delay can be adjusted from 0 to 165 milliseconds.

What Makes It Different

The DL207 provides configuration and calibration functions beyond basic loop amplification. Adjustable settings include input mixing, parametric equalization, compression, metal-loss compensation, high-pass and low-pass filters, automatic gain control, audio delay and output levels. Internal tools include a test-tone generator with pink noise, plus loop-current adjustment and matching. Configurations can be saved and loaded, and the system includes loop testing, priority-input selection with an adjustable threshold, open-circuit and short-circuit protection, and thermal protection.

A loop fault relay provides external fault signaling with contacts rated at 2.0 A at 30 VDC. Listed approvals include CE, UL, ULC, FCC, Industry Canada, RoHS, WEEE, CB Scheme and RCM. Test specifications are provided to IEC 62489-1. These monitoring, calibration and standards-oriented features make the DL207 particularly relevant where installation control and commissioning tools are important.

Final Assessment

The Williams AV DL207 SYS brings together dual-channel loop amplification, broad input compatibility, Ethernet-based control and built-in calibration tools in a compact rackmount format. Its published coverage, 9.5 Arms-per-output rating and configurable audio processing address medium-area T-coil support installations. A two-year warranty against component failure and manufacturing defects completes the supplied specification.