Multi-Tech Systems 7500, 7600 manual RS-485 Connections, Specifications are as follows

ION 7500 / ION 7600 User’s Guide COM1 Port

RS-485

COM

SH + --

External Modem Connections

Specification	Description
Cable Type	Standard straight-through RS-232 cable
Cable Ends	DB9 female end for mating with the DB9 male connector on the meter
Max. Cable Length	50 feet (15.2 m)

RS-485 Connections

RS-485 connections are made via the captured-wire connectors on the rear of the meter. Devices can be connected in series using RS-485 (see diagram to the left). Be sure not to ground the wires at both ends.

Specifications are as follows:

Specification	Value
Baud Rates	300 to 57,600 bps (default is 9,600 bps)
Duplex	Half
Supported Protocols	ION, Modbus RTU, DNP 3.0, FACTORY, Iec870-102, GPS: Arbiter,
	GPS: TRUE TIME DATUM, EtherGate, ModemGate (default is ION)
	Optical isolation from all other inputs and outputs (the COM1 RS-485 port
Isolation	is not isolated from the COM1 RS-232 port); isolation voltage is 750 V
	peak for 10 seconds @ 60 Hz.

Connections

Specification	Description
Cable Type	Good quality shielded twisted pair cable, AWG 22 or larger.
Max. Cable Length	4,000 ft. (1219 m) 1
Max. number of	32
devices per bus

1The lengths of all (+ and –) cable segments must be counted including those that connect devices to terminal blocks.

Terminal connections on the meter are marked as follows:

Marking	Terminal Function
SHLD	RS-485	Shield
–	RS-485	Data Minus
+	RS-485	Data Plus

Chapter 6 - Hardware Reference Page 165