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3. APPLICATIONS
56/64 Kbps Digital Line
38687
POWER
LOOPBACK
SIG
SYNC
XMT
RCV
BUSY BUSY
VOICE/DATA CSU
TxD
RxD
RTS CTS
38687
POWER
38687
Voice/Data CSU
LOOPBACK
SIG
SYNC
XMT
RCV
BUSY BUSY
VOICE/DATA CSU
TxD
RxD
RTS CTS
38687
Voice/Data CSU
Remote Site
Main Site
Typical Installation
Figure 1
The 38687 Voice/Data CSU provides end-to-end connectivity for one voice circuit and one data circuit
over a standard 56 Kbps or 64 Kbps digital telephone line, such as provided by local telephone companies
(Basic Digital Services), and long distance carriers (Digital Data Service, Accunet Spectrum of Digital
Services, etc). In these applications, the 38687 operates in "looped" timing mode, deriving its timing
from the network for purposes of synchronization. Connection to the network is via a standard RJ-48S
type modular jack.
The 38687 connects to DTE (Data Terminal Equipment) via the DB-25 interface connector mounted
on the rear panel of the unit. The DTE can be one of many devices, such as computer mainframes, minicomputers, workstations, CAD/CAM equipment, multiplexers, LAN bridges, video display terminals, video
conferencing equipment, high speed printers, etc. Typical applications include connection of terminals at a
remote location to a mainframe at a central location, or connections of a remote PC to a LAN. See
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