Lectrosonics DMTH4 – Telephone Interface and Digital Matrix Processor Lectrosonics

The DMTH4 integrates telephone lines, video codecs and external audio sources into the digital bus structure of DM Series processors so these sources operate as though they are another microphone or audio input in the sound system. The unit is much more than just a telephone interface. Instead, it is a complete DM Series digital matrix processor, with a 3-in/24-out digital matrix, automatic mixing and comprehensive signal processing on every input and output. In essence, it simply connects to telephone lines, video codecs and external audio sources instead of mic/line inputs and outputs and integrates seamlessly with DM Series matrix processors.

The primary applications are in sound reinforcement and conferencing systems in boardrooms, courtrooms, worship centers, distance learning systems, hotels and other applications with multiple microphones and loudspeakers. The design represents a milestone in DSP technology in its basic architecture and in its processing speed and efficiency.

The challenge in teleconferencing using a sound system on one or both ends of a conference is to minimize echo heard at the far end caused by the coupling between loudspeakers and microphones in the local sound system. As sound from the far end enters the local sound system and is delivered by the loudspeakers in the local room, it will enter the local microphones and be sent back to the far-end. At the far-end the listeners will hear an echo of their own speech. The integration of adaptive gain proportional auto mixing* with an all new proprietary acoustic echo canceller provides a remarkable solution that is as easy to install and set up as it is effective. Echo-free teleconferencing and clean local sound reinforcement is provided even in poor acoustical environments.

*US Patent 5,414,776

• 3-in/24-out digital matrix architecture
• Fully integrates with DM Series processors
• Telephone, codec and auxiliary inputs and outputs
• Two Acoustic Echo Cancellers – 126 ms tail time
• Line echo canceller – 30 ms tail time
• 6 filters plus compressor on each input
• 6 filters plus compressor/limiter on each output
• USB and RS-232 interfaces for setup and control
• Fully balanced audio signal flow through entire system – no pin 1 problem
• Digital I/O ports for daisy chaining and to connect other LecNet 2 devices
• Proportional gain auto mixing algorithm with AutoSkewª – US Patent 5,414,776
• Simultaneous LecNet2 and Third-Party control

The DMTH4 shares the large digital matrix bus with other DM Series processors to handle a wide range of sound system requirements from a modest boardroom to large systems with hundreds of inputs. Multiple units can be stacked with multiple DM processors to handle very large systems with multiple phone lines.

Extensive control capability is built into the unit with an intuitive command structure to allow external control with USB or RS-232 connections. Up to 128 macros can be stored in internal memory. Each macro can contain up to 64 commands, with 115 characters in each command. A built-in macro recorder greatly simplifies the creation of and use of macros.