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6/7/2007
724-746-5500
#22505
Technically Speaking
Time-division multiplexing.
TDM operates by dividing the available bandwidth into
fixed-duration segments. Each segment or channel is assigned
to a user and is given its own time slot to access the network.
First, information from Channel A is transmitted, then
information from Channel B, and so on in a regular sequence,
continually cycling back to Channel A. Bandwidth allocation is
static: Each channel receives a fixed amount of bandwidth,
preset by the network administrator.
TDM is a relatively inexpensive multiplexing technique and
is simple to implement, so it has typically been the first
multiplexing technique applied to any new high-speed
38892-R2
bandwidth service at first offerings. TDM introduces very little
signal delay, so it's well suited to transport data, voice, and
video traffic, provided enough bandwidth is available.
The figure on page 2 shows a mux merging 16 data
channels over dual fiber optic cable. Each data channel can
achieve speeds of up to 19.2 kbps with the 38892-R2 or 38890-
R2, 64 kbps with the 38888-R2.
Technically Speaking
Why choose fiber?
Fiber optic cable offers several clear advantages over
twisted-pair:
•
Using fiber completely eliminates the potential for
ground loops and electrical problems like crosstalk
(interference from an adjacent communication
channel).
•
With fiber you also get more bandwidth and speed, as
well as longer distances, which means more data goes
farther faster.
blackbox.com
TECH SPECS
Maximum Distance — 10,000 ft. (3048 m) over duplex multimode fiber
Multiplexing Technique — Time-division
Operation — Full duplex
Protocol — Async
Speed — 38892-R2, 38890-R2: 19.2 kbps;
38888-R2: 64 kbps
Interface — Channel: RS-232;
Composite: Dual ST
®
Connectors — Composite: All: (2) ST;
Channel: 38888-R2: (4) RJ-45;
38890-R2: (8) RJ-45;
38892-R2: (16) RJ-45
Indicators — (3) LEDs: Power, Composite Data, Sync Loss
Power — 115-VAC, 60-Hz external power supply
Size — 38888-R2, 38890-R2: 1.7"H x 7"W x 5.3"D (4.3 x 17.8 x 13.5 cm);
38892-R2: 2.2"H x 7"W x 5.3"D (5.6 x 17.8 x 13.5 cm)
Weight — 38888-R2, 38890-R2: 2 lb. (0.9 kg);
38892-R2: 2.5 lb. (1.1 kg)
Item
Async Local Fiber Optic RS-232 Multiplexor
4-Port
8-Port
16-Port
Optional accessories include...
Telephone Bulk Cable
Fiber Optic Duplex Bulk Cable
Modular Adapters
DB25 Male/RJ-45 for DTE
DB9 Female/RJ-45 for DTE
DB25 Female/RJ-45 for DTE
DB25 Male/RJ-45 for DCE
Code
38888-R2
38890-R2
38892-R2
EL08A
EXN062A
523951
523953
523954
523952
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