S1-6
:
Receive Impedance
: Selects the impedance of the input receiver. You may select either
a "low" impedance or 120 ohms or a "high" impedance of 16K ohms. By selecting the proper
impedance for each drop, you can have up to 50 receivers in one application. The Master and
the last slave should be set for low impedance. Any drops in between them should be set for
high impedance.
S1-6
Setting
ON
Low (120 ohm) Terminated
OFF
High (16 K) Unterminated
S1-7 and S1-8
:
2-wire/4-wire Modes:
Both switches are set together to determine whether
the Driver is in 2- or 4-wire operating modes. Note: 2-wire is half-duplex only.
S1-7
S1-8
Setting
ON
ON
2-wire mode
OFF
OFF
4-wire mode
Configuration Switch Applications
:
The table to the left shows you how to set the Driver's configuration switches to fit several
common applications. If you have any questions about the proper settings for you application,
call your supplier.
When You're Finished Configuring:
Once you've finished setting the Mini Driver MP's configuration switches, pause before you
snap the case halves back together. Make sure you have the 4-wire connected to the terminal
blocks set correctly.
INSTALLATION:
Once you've set the configuration switches, you're ready to connect the Driver to your
system. This section tells you how to properly connect two or more Drivers to each other and to
the RS-232 interface.
Twisted-Pair Connection:
Keep these points in mind as you connect the twisted-pair side of the Driver:
The Driver operates over one or two metallic twisted pairs--two or four wires. The wires must be
dry, unconditioned metallic wire between 19 and 26 AWG (lower-number gauges allow the
longest distances). Standard dial-up telephone circuits, or leased circuits that run through signal-
equalization equipment, are not acceptable.
The units must be used in pairs--one at each end of the twisted-pair line. In multipoint
environments, there should be one Driver at the RS-232 host and one at each RS-232 terminal.
Terminal-Block Twisted-Pair Connection:
If your application requires you to connect one or two pair of bare wires to the Driver, you'll
need to get into the internal terminal blocks. In a two-pair circuit, connect one pair of wires to
XMT+ and XMT- (transmit positive and negative) on the terminal block, making careful note of
which color is positive and which color is negative.
Connect the other pair of wires to RCV+ and RCV- (receive positive and negative) on the
terminal block. Again make careful note of which color is positive and which is negative. Your
completed cross-over cable should be pinned electrically as follows:
XMT +
RCV +
XMT -
RCV -
RCV +
XMT +
RCV -
XMT -
In a single-pair circuit, use only the transmit (XMT) pair as follows:
XMT +
XMT +
XMT -
XMT -
If there is a shield around the telephone cable, it may be connected to "G" on the
terminal block. We recommend connecting the shield at the computer end only to avoid
ground loops.
A ground wire is not necessary to properly operate the Driver.
POSITION
FUNCTION
FACTORY DEFAULT
S1-1
S1-2
"Transmit OFF" Impedance
"Transmit OFF" Impedance
OFF
High Impedance
OFF
S1-3
RTS/CTS Delay
ON
8 msec.
S1-4
Echo Mode
OFF
Echo OFF
S1-5
Carrier Control
OFF
Constantly ON
S1-6
Receive Impedance
ON
120 Ohms
S1-7
S1-8
2-wire/4-wire
2-wire/4-wire
OFF
4-wire
OFF
DB25M/F CONNECTOR
+ RCV - G + XMT -
DB25M/F CONNECTOR
+ RCV - G + XMT -
4-wire Full Duplex
DB25M/F CONNECTOR
+ RCV - G + XMT -
DB25M/F CONNECTOR
+ RCV - G + XMT -
2-wire Half Duplex
