DATA-LINC GROUP
3
MDL500 User Guide
PN 161-10003-002B
rev 8/03
Introduction
The Data-Linc Group MDL500/MR is a two-wire private line modem. The MDL500/MR allows 9600 baud full and half-duplex
RS232 data communications over a single dedicated wire pair and across sliding contacts. The MDL500/MR operates using
pure Frequency Shift Key (FSK) at high carrier frequencies (100 KHz, 106.5 KHz to 150 KHz, 156.5 KHz) making the
MDL500/MR particularly immune to cross-talk and outside noise interference. This provides highly reliable, continuous data
transmission over distances of several miles in harsh industrial environments.
The Data-Linc MDL500/LR is a four-wire private line, long range 9600 baud full-duplex modem. In four wire LR operation, the
typical range on 22 gauge communication wire is 8 to 10 miles.
Transmission
The MDL500 performs data communication by converting digital signals to modulated high frequency sine-wave carrier
signals that can be transmitted much longer distances with greater noise immunity on wires than square wave digital
signals. The digital Space and Mark (or 0 and 1) are converted in the transmitter to carrier signals having two slightly different
frequencies which are identified by the receiver and reconverted to the digital signals. The MDL500s are either Master or
Remote units and can be used for either point-to-point or multi-point communications. The MDL500s are asynchronous serial
data communication devices, data rate transparent from DC to 9600 baud.
In multi-drop installations, the modems can be connected in a star or daisy-chained. The master modem can be located at
any of the connection points.
RS232 Interface
The MDL500 connects to the user provided equipment via an industry standard, female DB25 connector conforming to the
IEEE RS232C standard. The modem can be configured to function as either a DCE or DTE interface.
Data-Linc Group provides cables and/or pinouts for connecting the MDL500 to a wide variety of electronic devices. Contact
our technical support staff for cable specifics.
MDL500 Master Units
The MDL500 Master unit transmits at 106.5/100 KHz (Space/Mark) and receives at 156.5/150 KHz. A pluggable two position
terminal block at the back of the unit is used for non-polarized connection to the transmission line.
MDL500 Remote Units
The MDL500 Remote unit transmits at 156.5/150 KHz and receives at 106.5/100 KHz. It has the same data line connector
as the Master unit.
