Architectural and Engineering Specifications
Sound Choice Assistive Listening, Inc. model SC-186Kx2

The transmitter shall operate by means of infrared light carriers frequency modulated by an audio source. The optical carriers shall operate at center frequencies of 2.3 megahertz and 2.8 megahertz. The infrared light wavelength shall be centered at 880 nanometers. The transmitter shall incorporate a self-contained infrared emitter system generating a main forward beam with a dispersion of 120 degrees and a radiated optical power greater than 450 milliwatts.

The transmitter shall include a built-in electret condenser microphone of the boundary effect type also commonly known as a pressure zone microphone. The transmitter shall also include self-contained audio circuitry comprising a preamplifier capable of gain greater then 50dB (decibels), a high pass rumble filter, mid/high-frequency boost equalization, an automatic gain control/peak limiter.

There shall be a 1/4 inch (6.5 mm) external input jack switchable for mic or line levels. Said switch setting shall have no effect on the integral transmitter microphone when the jack is not used. Plugging an external source in the jack will automatically disconnect the internal microphone. There shall also be a 1/4 inch (6.5 mm) line output jack for transcription recording.

The transmitter will optically transmit audio from the onboard microphone, or from an external microphone or line source, simultaneously on both audio frequencies (2.3 mHz and 2.8 mHz). There shall be provisions for a wired remote privacy mute switch which will only mute the audio signal transmitted on the 2.3 mHz channel. The 2.8 mHz channel shall remain un-muted at all times.

There shall be provision for a secondary combined microphone/infrared emitter device connected as a part of the transmitter system. This device will provide a second boundary effect microphone operating concurrently with the primary integral transmitter microphone. The secondary microphone enclosure shall also provide a secondary infrared optical emitter array transmitting simultaneously with the main emitter array when connected. The combination microphone and optical emitter array shall connect to the main transmitter’s “slave” jack via a 6 foot (approximately 2 meter) cable.

Power shall be supplied by a UL approved AC wall outlet transformer. There shall be a power switch on the transmitter panel with a power indicator light. The exterior frame of the transmitter enclosure shall be of finished natural wood and will have external dimensions of 6 1/2 inches by 5 inches by 1 3/4 inches high (16.5 cm x 12.7 cm x 4.5 cm).

The Sound Choice Model SC-186Kx2 Infrared Audio Transmitter is specified