Multi-Tech Announces Voice/Data/Fax MultiMux Priority Statistical
Multiplexers (PSMs)

MOUNDS VIEW, MINNESOTA--November 15, 1993--Multi-Tech Systems Inc., a
leading data communications technology company, announced adding voice and
fax capabilities to selected models of its high-speed Priority Statistical
Multiplexer (PSM) line. The MultiMux MMV1600 and MMV3200 series high speed
multiplexers now support two voice/fax channels over composite links that
can operate up to 256K bps when connected to appropriate external DSUs.
Each channel includes connector/interfaces for FXO, FXS and E&M operation.
The MultiMuxes operate over a single composite link at up to 256K bps or
dual composite links at up to 128K bps. Dual composite link configurations
are used for interconnecting several sites to form private multi-node
networks. The 1600 and 3200 series MultiMuxes provide synchronous,
error-free data transmission between nodes with data encryption security.
Each includes a built-in command modem for easy network management.
MultiMuxes also can be equipped with internal or external DSUs which are
ideally suited for use over AT&T's DATAPHONEX Digital Service (DDS) or
equivalent digital data services. Retail prices range from $4599 (U.S.)
for the Model MMV1608C/2, which provides up to 8 channels (expandable to
16), two voice/fax channels (MV2 card), and two digital composite links
(DSUs not included), to $10899 (U.S.) for the Model MMV3232C/56/56/2,
which provides 32 data channels, two voice/fax channels, and two digital
composite links with integral multi-rate 56K bps DSUs. MMV series
MultiMuxes also can be field upgraded with the MV2 2-channel voice card
priced at $1400 (U.S.). MV2 voice cards will be available for shipment
first quarter of 1994.

"The basic reason for adding voice and fax communications to multiplexer
lines is to save on phone charges. By doing so, you are getting virtually
free phone calls and fax transmissions between locations networked with
voice/data/fax muxes. You need to select the right technology at the right
price to get the best price while not sacrificing quality in your voice
communications," states Raghu Sharma, President of Multi-Tech Systems,
Inc. "Our combination of two voice/fax channels for $1400, a multiplexing
technique superior to Time division Multiplexing (TDM), and voice
compression that gives you better quality than the competition makes the
Priority Statistical Multiplexers a cost effective addition to your
network."

With the addition of voice and fax information streams to Statistical Time
Division Multiplexers (STDMs), an added technology needed to be
incorporated to accommodate the time-sensitive nature of both voice and
fax transmissions. We call that technology Priority Statistical
Multiplexing (PSM). With PSM, data packets are of limited length and
voice/fax packets are given priority. The length of the data packets are
determined dynamically according to the link speed preserving the timing
requirements of normal speech and non error correcting fax
transmissions."

PSM also facilitates an efficient means to network voice/fax/data packets
between dual composite linked MultiMuxes connected in various locations.
That is because a PSM packet which is received by a MultiMux node and must
be passed to another node can be routed directly without a "store and
forward" step usually associated with STDM technology. PSM provides only
end-to-end error detection/correction (i.e. intervening nodes only relay
packets) which decreases the end-to-end packet delay. Since MultiMuxes can
automatically determine whether a transmission is voice or fax, PSM links
between nodes can handle both data and fax transmissions eliminating the
need to dedicate links.

PSM is a very simple extension of STDM technology. What is not simple,
however, is the voice compression technology to get clear speech over such
a packet network. With many other competitive products, the compression
used is simply Adaptive Differential Pulse Code Modulation (ADPCM), which
can be done at 32K or 16K bps. At 16K bps the resulting voice quality is
marginal. Multi-Tech has developed an algorithm for compressing speech to
16K or 9.6K bps bandwidth based on Vector Quantization, which provides
superior quality when compared to ADPCM samples using the same bandwidth.
Instead of encoding the speech waveform on a sample-by-sample basis, as in
ADPCM, Vector Quantization works with blocks of samples matched to vector
table values which most closely match the waveform.

The new MMV1600 series MultiMuxes provide 8 or 16 asynchronous data
channels to which two voice channels can be added via the MV2 board. The
V.35 or RS232-compatible dual composite links can operate with either
external 4-wire synchronous modems, or external DSU/CSUs up to 256K bps.
The MMV1600s can be equipped with internal DSUs designed for operation
over AT&T's DATAPHONE Digital Service (DDS) or equivalent digital data
services. All MultiMuxes come equipped with an internal 2400 bps command
modem which can be used to remotely manage, test and maintain MultiMux
nodes. The muxes feature input channel speeds up to 19.2K bps,
asynchronous data input, a networking feature, hardware and software flow
control, EIA pass-through, downline parameter loading, channel pacing,
operational statistics, and full system diagnostics,.

The MV2 voice/fax board provides two channels with all the necessary
interfaces to access PBX and telephone services. Each channel has two RJ11
connectors for FXO ( PBX station side) and FXS (e.g. telephone set), and
one RJ48 for E&M I, II, III, IV, and V PBX interfacing. The MV2 is totally
software configurable for selecting items such as compression rate,
interface type, volume control, voice link selection and destination. The
MV2 board also can be field retrofitted in MMV1600 and MMV3200 series
MultiMuxes.

Multi-Tech Systems, which reported sales of $81 million for 1992, was
founded in 1970 to manufacture data communications equipment and systems
for the global market of networking product users. The Minnesota-based
company is well-known for its MultiModem line of dial-up communications
products. Multi-Tech's family of products include a complete line of
data/fax modems, MultiMux statistical multiplexers, DSUs, 3270/3780/5250
emulation systems, X.25 PADS/switches, UNIX serial interfaces,
communications software, LAN/WAN connectivity products, and most recently,
the MultiModemPCS, a voice/data/fax personal communications system. These
products are sold in over 70 countries through a worldwide network of
distributors, manufacturer's reps, systems integrators, value-added
resellers (VARs) and retailers. Multi-Tech Systems Inc. can be contacted
at its headquarters: 2205 Woodale Drive, Mounds View, Minnesota 55112.
Voice (612) 785-3500 or (800) 328-9717, FAX (612) 785-9874, International
FAX (612) 331-3180, Telex 4998372MLTTC.

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