Data-Linc Group MDL500/MR Panduan Pengguna - Halaman 11

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General Operating Notes

The MDL500/MR utilizes tuned circuits to achieve high performance. These circuits have been carefully adjusted at the

factory to operate over several miles of transmission line. In order not to degrade performance, it is important not to disturb

these adjustments. In particular, coils T1, T2, T3, T4 and T5 and potentiometers R18, R20, R31 and R57 should not be

adjusted. If these adjustments have been inadvertently changed, please contact the factory.

Non-Loaded Transmission Line

Proper operation of MDL500/MR requires that the transmission line be non-loaded (free from inductors and capacitors on the

line). The presence of inductors, capacitors or excessive resistance (i.e., bad connections) or shorts between the wires can

seriously degrade performance or render the data transmission inoperable.

Loop Back Test

A Loop Back test is suggested to confirm the proper operation of MDL500/MR's in point-to-point operation, as follows:

A PC running a communication program in full-duplex can be connected to one of the MDL500/MR'S in a point-to-point

configuration. A jumper wire (a bent paper clip works very well) is placed between pin sockets 2 and 3 of the DB25 on the

other MDL500/MR. Data sent to the first MDL500/MR will be looped back from the second and appear on the PC screen. If

the characters are correct, the MDL500/MR's are functioning.

AE485 Interface

The MDL500 is also available with an RS485 interface for connection to multiple Remote devices. All operating functions and

instructions are the same as for the RS232 full-duplex version, except that the digital interface through the DB25 connector

uses pin 12 as the -DO/RI connection and pin 13 as the +DO/RI connection. The RS232 connections (pins 2, 3 and 7) are

not functional.

Note: Do not connect anything except an RS485 signal to positions 12 and 13 on the DB25 or damage

to the circuit could occur.

The Data-Linc Group AE485 (Auto Enable) circuit contains a special feature that eliminates the need for a separate enable

signal or line to command the 485 transmit and receive functions. Data will pass through the MDL500 RS485 port

transparently in either direction. The MDL500s are operated in full-duplex point-to-point mode (no carrier control) when using

the AE-485 interface. Up to 32 Remote RS485 devices can be multi-dropped off the MDL500 AE485 port at distances of up

to 4000 feet and at data rates of 9600 baud. A 100 ohm termination resistor should be connected at the ends of the 485 line.

PN 161-10003-002B

rev 8/03

DATA-LINC GROUP

MDL500 User Guide