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CHAPTER 2: Introduction
2. Introduction
The RS-232 Synchronous Multipoint Line Driver provides short-haul synchronous
data communication over customer-owned twisted-pair cable. It’s available as a
standalone unit (Part Number ME742A-R3) or a rackmount card (Part Number
ME742C-R3). The rackmount version is functionally identical to the standalone
unit, but it fits in a rackmount chassis that holds up to 16 cards. Each Line Driver
comes with a 6-ft. DB25 male to DB25 male RS-232 extension cable and a DB9
female to DB25 male adapter.
The LD485S has an RS-232 port (configured as DCE) that connects to a host
computer or terminal (DTE), and a 4-screw terminal block for RS-485
communication over a 2- or 4-wire line. Transmission can be two-wire half duplex,
or four-wire half/full duplex. There are a variety of switch-selectable baud rates
ranging from 1200 to 128,000 bps.
A group of LEDs on the unit’s front panel indicate flow-control status (TX, RX,
RTS, CD). Three pushbuttons on the front panel are used to perform line and
digital loopback testing. A number of options are configurable via internal switches
or jumpers:
• Data rate
• Constant Carrier/Switched Mode with selectable RTS/CTS delay
• Full/half duplex
• TX data clock select
• Node termination
• Frame ground/signal ground
