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Configuring Modems and HDLC Cards
This chapter covers these topics:
Introduction
This section describes the following types of cards.
Series56 Digital Modem card
Each MAX TNT Series56 Digital Modem card provides forty-eight V.34 and K56flex-compatible digital modems, which can receive or place analog and digital calls. The card can support analog or cellular connections at speeds of up to 56 Kbps. It enables remote users with a modem and an analog or cellular line to dial into the MAX TNT via T1 access lines. The Series56 Digital Modem card is dual-height, meaning that it occupies two MAX TNT expansion slots. You can install a maximum of 6 Series56 Digital Modem cards in a single MAX TNT shelf.
Figure 6-1. Series56 Digital Modem card
Digital Modem card
Each MAX TNT Digital Modem card provides forty-eight V.34 Digital modems, which can receive or place analog and digital calls. The card can support analog or cellular connections at speeds of up to 33.6 Kbps. It enables remote users with a modem and an analog or cellular line to dial into the MAX TNT via T1 access lines. The V.34 Digital Modem card is dual-height, meaning that it occupies two MAX TNT expansion slots. You can install a maximum of 6 Digital Modem cards in a single MAX TNT shelf.
Analog modem card
Each MAX TNT Analog Modem card provides 36 analog modems, which can receive analog calls. The card can support analog or cellular connections at speeds of up to 33.6 Kbps. It enables remote users with a modem and an analog line to dial into the MAX TNT via analog lines. The Analog Modem card is dual-height, meaning that it occupies two MAX TNT expansion slots. You can install a maximum of 6 Analog Modem cards in a single MAX TNT shelf. 
Installing modem cards
You install modem cards in the same way you install other MAX TNT slot cards. For information about installing MAX TNT slot cards, see Installing a slot card.
Overview of configuring modem cards
Typically, digital modems do not require any configuration. Depending on your network setup, however, there might be situations that require you to change how the modems operate. When you make a change to the modem configuration, it applies to all the modems in the MAX TNT. You can configure the MAX TNT modems in the Terminal-Server profile.
For complete information about the associated parameters see the MAX TNT Reference Guide.
Specifying negotiation settings
Calls from analog modems are directed first to the MAX TNT digital modems, where the connection must be negotiated before being directed to by the terminal-server software. Options in the Terminal-Server > Modem-Configuration subprofile allow you to modify how the MAX TNT digital modems negotiate a connection.
admin> read terminal-server
TERMINAL-SERVER read
admin> list modem-configuration
v42/mnp = will-v42
max-baud-rate = 33600-max-baud
modem-transmit-level = -13-db-mdm-trn-level
cell-mode-first = no
cell-level = -18-db-cell-level
7-even = no
V.34 setting for 56k modem cards
You can configure the MAX TNT Series56 modems to use V.34 modem modulation. To support the ITU-T standard V.8bis (Voice Call Ready), a 56K modem in the MAX TNT normally sends a tone at the beginning of modem training. This is commonly referred to as CRe and is a dual tone (1375Hz + 2002 Hz) followed by a single tone at 400Hz with a combined duration of approximately 500 ms. Although V.8bis is designed not to interfere with V.32bis modem negotiation, some V.32 and V.34 modems do not successfully complete modem training after reception of the V.8bis tone.
admin> read terminal-server
TERMINAL-SERVER read
admin> set modem-configuration modem-mod = v34-modulation
admin> write
TERMINAL-SERVER write
Hybrid Access card
The Hybrid Access card, also referred to as the HDLC card, provides support for 128 HDLC sessions. This section explains whether you need a Hybrid Access card and also explains how nailed channels use the HDLC channels on the Hybrid Access card. Do you need a Hybrid Access card?
Each ISDN call, and each channel of a nailed session, requires an HDLC channel to process the HDLC-encapsulated data received from or destined to a WAN interface. Because the MAX TNT base system does not provide any HDLC resources, you might need to install a Hybrid Access card in your unit.
Therefore, how many nailed sessions a single HDLC card can support depends on how the channels are configured in each connection. For example, if you have five nailed T1 connections (of 24 channels each), each of which requires an HDLC resource, 8 HDLC resources are still available on the HDLC card. These resources can be used for 8 switched connections, or for any combination of nailed channels and switched channels as long as each nailed line contains less than eight channels.
For example, the DS-3 card can provide up to 28 full T1 (24 channel) nailed connections. Each HDLC card can support up to five full T1s, so six HDLC cards are required (28 T1 lines / 5 lines per HDLC card=5.6 HDLC cards).
Installing the Hybrid Access cards
You install Hybrid Access cards in the same way you install other MAX TNT slot cards. For instructions, see Installing a slot card.
Copyright © 1997, Ascend Communications, Inc. All rights reserved.