DATA-LINC GROUP
8
PN 161-10003-002B
rev 8/03
MDL500 User Guide
MDL500/MR/LR Four-Wire Special Instructions
The standard instruction “MDL500 Industrial Modem Half and Full-Duplex Versions” are applicable with the following
modifications:
MDL500/MR/LR Four-Wire Long Range Transmitter & Receiver Jumpers
The transmitter output is set to high by placing the jumper located on the three pin mail header marked “TP2” in the left and
center position (left side on the marking TP2). The receiver gain is set on medium by placing the jumper on the four pin male
header (inverted T-shape) located above T5 and C35 on the bottom center (marked G2) and pin between R53 and R55.
Note: The header position locations described are with the MDL board oriented with the LED’s to the left, the
connectors to the right.
MDL500/MR/LR Four-Wire Long Range Carrier Signal Connectors
The four-wire MDL has a second I/O isolation coil and a second two-position pluggable terminal block for the transmitted
carrier. Facing the connectors, the pluggable terminal block on the left is the transmitted carrier and the pluggable terminal
block on the right is the received carrier.
For proper operation, both modems must be set to the same four-wire configuration.
Front Panel LEDs
There are four LED’s on the front panel of the MDL. From left to right:
The first diagnostic LED is Carrier Detect. In full-duplex mode, the CD LED must be lighted on both units. In half-duplex
operation with the Master carrier on and the carrier control mode with RS232 cables connected, the CD LED will be lighted
on all Remote MDL500/MR’s and OFF on the Master MDL500/MR. (The Master CD LED will blink during operation as each
Remote MDL500/MR turns on its carrier to answer back to the Master). If the correct CD LED’s are not ON, a carrier cable
problem is likely.
Assuming that the CD indication is correct, a Loop Back test is recommended as described on the next page.
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