Specifications

Table Of Contents

70 AR Router

C613-03058-00 REV A

Transition cables can be changed at any time. It is not necessary to power-down

the router.

When an RS-232 DCE transition cable is connected to a synchronous interface

configured to generate clocks, the maximum clock speed is 38400 bps. When an

X.21 DCE or V.35 DCE transition cable is connected to a synchronous interface

configured to generate clocks, the maximum clock speed is 2 Mbps.

Modems and NTUs

Modems and NTUs are used to transfer digital information over wide area

Telecom links. Strictly speaking, a modem is an analog device, while an NTU is

digital device.

Modems can be either asynchronous or synchronous. The distinction is that

synchronous modems provide a bit clock for both transmitted and received

data, while asynchronous modems don’t require a clock and rely on the

inherent framing provided by the start and stop bits. Normally, any modem

9600 bps or faster will be synchronous. The router can be connected to other

remote routers to form a wide area network (WAN), using synchronous

modems connected to the synchronous interfaces on the router’s rear panel.

WAN links faster than 9600 bps are normally provided using Network

Terminating Units (NTUs), which are always synchronous. The interface to

these devices is generally X.21 or V.35.

Good quality data grade cables should be used for all cables, particularly X.21.

This must be made from paired cable with an overall foil shield. Ideally,

metalised backshells should also be used. Poor quality cables will limit the

maximum speed or the maximum length of the cable, or both.

Ethernet Interfaces

10BASE-T Interfaces

All AR300 Series routers have at least one 10BASE-T Ethernet LAN port. The

AT-AR330 has two 10BASE-T Ethernet LAN ports. A rear panel slide switch

(labelled MDX) allows the user to configure the LAN port for a direct

connection to either a hub or personal computer. The same RJ-45 cable

(supplied with the router) may be used in either situation.

The LAN ports can easily be tested using a simple external loopback plug. See

“Cables And Loopback Plugs” on page 75 for details of how to construct a

loopback plug.

10BASE-T/100BASE-TX Interfaces

The AT-AR026 4ETH PIC has four 10BASE-T/100BASE-TX ports with RJ-45

connectors. Port characteristics such as speed, flow control, half/full duplex,

and auto-negotiation can be set by configuring links on the PIC’s PCB. See the

PIC Hardware Reference for more information. If your router has a PIC bay, the

PIC Hardware Reference is included on the Documentation and Tools CD-ROM

that shipped with your router, or it can be downloaded from