Data-Linc Group MDL500/MR Manuel de l'utilisateur - Page 6

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MDL500 User Guide

Power Source

The MDL500 is powered by nominal 24 volts DC which is supplied to a black barrel jack on the rear panel. The units are

delivered from the factory with 120 VAC to 24 DC wall transformers, which have a black plug attached. An external 24 VDC

supply can also be used to power the MDL. The current draw is 250 mA.

Caution: Ensure the unit is disconnected from power before removing the cover.

Operating Modes

The MDL500 can be operated in either point-to-point or multi-point polling modes. In point-to-point, the modems can be

operated in full-duplex.

For multi-point data communications, the MDL500 can be operated with one Master and up to eight Remote units. The

connected intelligent device controls the transmitter in each Remote unit. The Master unit's transmitter remains on at all

time; however, only one slave transmitter can be active at any given time. Multi-point systems must e operated in a half-

duplex mode.

For four wire MDL500 operation, see the section on MDL500/MR/LR Four-Wire Special Instructions.

Installation

The MDL500 factory configuration is set for full or half-duplex point-to-point operation with P4 in the B-C position. The Master

and Remote units are both factory configured as DCEs (Data Communications Equipment) with the jumpers on headers P1

and P2 in the B-C position. Data into the DB25 is on pin 2 and data out is on pin 3. (Also see section 5.0, entitled Jumper

Settings.)

Prior to installation, it is important to ensure that the digital devices to be connected to the MDL500/MR units are capable of

communicating with each other as if connected with a conventional three-wire RS232 data cable. Once this has been

established, the devices can be connected to the MDL500/MR units and RS232 data communications will take place

transparently.

Note: It is important the wire pair to be used for data communications between the MDL500/MR units:

a) Is connected only to those units.

b) Has no branches and no attached inductance, capacitance or resistance.

c) Has no loading coals, filters or any other load.

d) And all connections must be clean and solid.

Note: Since the data line is transformer isolated from the rest of the circuit, neither leg of the data carrying twisted pair

should be grounded.

DATA-LINC GROUP

PN 161-10003-002B

rev 8/03