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Operation
Private Line Operation
The modem can be configured to operate over a point-to-point, unconditioned, voice grade private
line (speech band leased line). Point-to-point private lines rented from the telephone company are
dedicated, direct, semi-permanent phone line connections between two locations. In applications
that require a continuous data transfer between fixed points, it may be more economical to rent a
private line at a fixed rate, than to pay monthly long distance charges for dial up calls. The
communication link between two multiplexers will generally involve a modem operating over
private lines.
Note
Speeds below V.32 4800 bps are not supported in private line operation.
Two-wire Setup
The Dual V.34 modem is capable of operation on private line networks, using 2-wire circuits.
•
Use &L1 to select 2-wire operation.
•
For proper private line connection, the 8-pin cable should be used to connect the modem's PL
jack to the JM8 wall outlet supplied by your service provider.
•
When using Factory Default 0 (&F0) to set up a private line connection, make all other option
settings before issuing the &L1 command. The modem will begin its training sequence at once
when it is given the &L1 command.
•
To abort training sequence and return to Command mode you can either press the SEL button
three times or press the AL button.
Private Line Configuration
In any private line connection, first designate one modem as the originate modem (%O0) and the
other as the answer modem (%O1). Next, configure both modems for the type of communication
they are intended to perform: normal or reliable modes (\N command), synchronous or
asynchronous modes (&M command), DTE and VF modulation (\T and &P commands), etc.
Select &P0 (V.34 only), &P1 (V.32 bis only) or &P2 (V.32 only) to establish the desired modulation
in private line.
Note
If an error-corrected link is desired, configure the modem for
\N4
(V.42 (LAPM) reliable mode) rather than
Transmit Level
It is possible in private line operation for the transmit levels of the modems to be either too low or
too high. When that is the case the connection usually will not be dependable and will be filled with
errors. To correct such situations, the transmit level of the modem for private line operation can be
configured in 1 dBm increments between 0 dBm and -15 dBm. This selection is done with the :T
command. See Chapter 4, AT Command Set Operation for details.
Note
It is recommended that you permanently store the above settings by entering the
modems are now ready for private line communications. If the modem is switched between V.34 and V.32
bis/V.32 modes of operation, the local unit must be set to private line idle (
online command (
3-36
ATO
).
SpectraComm Dual V.34 Modem
Installation and Operation
Private Line Operation
\N2
(MNP reliable mode) or
\N3
(V.42/MNP auto-reliable mode).
+++
&W
command. The
,
ATH
) before issuing an
060R122-000
Issue 15
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