Netgear XM128 ISDN User Manual download pdf (Page 55)

Reference Guide for the Model XM128 ISDN Digital Modem

ISDN Overview 6-7

If an incoming setup message is offered with addressing information (that is, the appropriate part

of the Called Party Number), this address is compared with the MSN numbers assigned by the

AT&ZIn=s commands. The call is accepted using the specific protocol if the assigned number of

this protocol matches the received Called Party Number.

The called party subaddress information within the incoming setup message can also be

used to select the protocols and/or analog ports. In normal conditions, called party subaddress

information is not used by the Model XM128 modem to select the protocols or services, but only

indicates the subaddress (if any) to the DTE. Refer to Chapter 11 for more detailed information.

Data over Speech Channel

If you are expecting ISDN data calls through Speech (Voice) channel, you would need to set up

MSN for it. If no MSN entries are found in MSN ISDN data lists, all speech (voice) calls are sent

to either PHONE 1 jack or PHONE 2 jack. The entry to use would depend on the type of data call

that you are expecting. If you expect only PPP type of calls, you should enter the number that the

remote user used to dial in to entry #3 (AT&ZI3=xxx) or entry #5 (A&ZI5=xxx). After this

number is set, when the caller dials in to this number, the Model XM128 modem attempts to use

PPP protocol to handshake with this remote user. This handshake takes place whether the setup

message from the switch indicates an ISDN data call or a speech (voice) call.

Best-effort Call Answering

If some numbers have been set using &ZIn command (as can be seen by the AT&ZI? command)

and they are not matched with the address of the incoming call, the Model XM128 modem, by

default, ignores the call because it may be intended for other devices that share the same S/T

interface (S0 bus) with the Model XM128 modem.

Note:

You are not required to enter the complete numbering string for the AT&Z

command. The last few distinguishable digits are enough for the XM128 to make the

decision. Two phone number strings are said to be matched if their least significant n

digits are identical, where n is the number of digits in the shorter string.

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Netgear XM128 ISDN User Manual Page 55