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Term Main definition
Digital Service level 1. Digital service that provides 24 separate 64Kbps digital channels.
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DSX bay
A combination of the various pieces of DSX apparatus and its supporting mechanism, including its frame, rack, or other mounting devices.
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DSX complexes
Any number of DSX lineups that are connected together to provide DSX functionality.
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DSX lineup
Multiple contiguous DSX bays connected together to provide DSX functions.
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DU connector
A fiber-optic connector developed by the Nippon Electric Group in Japan.
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Dual ring
A pair of counter-rotating logical rings.
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Dual-attachment concentrator (DAC)
An FDDI concentrator that offers two attachments to the FDDI network that are capable of accommodating a dual (counter-rotating) ring.
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Dual-attachment station (DAS)
A term used with FDDI networks to denote a station that attaches to both the primary and secondary rings; this makes it capable of serving the dual (counter-rotating) ring. A dual-attachment station has two separate FDDI connectors.
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Dual-tone multifrequency (DTMF)
The signal that a touch-tone phone generates when you press a key on it. Each key generates two separate tones, one in a high-frequency group of tones and one from a low-frequency group of tones.
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Dual-window fiber
An optical fiber cable manufactured to be used at two different wavelengths. Single-mode fiber cable that is usable at 1300nm and 1550nm is dual-window fiber. Multimode fiber cable is optimized for 850nm and 1300nm operations and is also dual-window fiber. Also known as double-window fiber.
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(1) A single enclosed raceway for wires or cable. (2) An enclosure in which air is moved.
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(1) A link or circuit that can carry a signal in two directions for transmitting and receiving data. (2) An optical fiber cable or cord carrying two fibers.


(2) Duplex Leads – Also known as shotgun or dual

A double loom, two lengths of cable run together to simultaneously send (TX) and receive (RX) data.
If you have a communications line that lets you send and receive data (or talk and listen) at the same time, it's duplex. If you use a cheap speakerphone, you'll notice that as soon as it picks up any noise at your end, it cuts off whatever was being said by the person on the other end. That speakerphone is not duplex.

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Duplex cable
A two-fiber cable suitable for duplex transmission. Usually two fiber strands surrounded by a common jacket.
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Duplex transmission
Data transmission in both directions, either one direction at a time (half duplex) or both directions simultaneously (full duplex).
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Duty cycle
With respect to a digital transmission, the product of a signal
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