ISDN Data and Telephony Protocol Engine (inc. X.25)
CMX228
1.5.3.4 Incoming Calls
Incoming voice calls and calls from analogue lines are directed to the analogue port and all other
incoming calls are directed to the RS232 port.
1.5.3.5 Multiple Subscriber Numbering
Multiple Subscriber Numbering (MSN) enables each POTS or RS232 port of the CMX228 to have its
own telephone number. Up to 23 digits can be saved as the MSN for each port.
All incoming SETUP messages will be checked for the presence of a Called Party Number Information
Element (IE). If one is present it is compared with the saved MSN number (if present), starting with
the last digit of both numbers. Comparison continues until there are no more numbers in the MSN
saved number or the incoming Called Party Number or there is a difference between the numbers.
The MSN is said to match if the saved MSN and the incoming calls’ Called Party Number are the
same for the duration of the shorter number (ie if the digit ‘1’ is saved and the received Called Party
Number is 654321, then the MSN matches). If there is no saved MSN, the Called Party Number is
ignored and call processing continues.
When there is a saved MSN and the Calling Party Number transmit is enabled, all outgoing call
SETUP messages will contain a Calling Party Number Information Element.
Note 1: When a CMX228 with MSN saved and Calling Party Number transmit enabled is
connected to some exchanges, no dial tone is heard when going off-hook.
Note 2: Disabling the Calling Party Number transmit will mean that the called party may not
receive the Calling Line Identification (CLI), or if they do receive a CLI it will probably be
the base number and not the number specific to the calling telephone.
1.5.3.6 Channel Mapping
It is possible to configure the CMX228 so that analogue and/or digital ports will only originate calls to
and respond to calls from a specific ISDN B-channel. This is a useful feature if, for example, you wish
to have a hunt group on your ISDN line (ie to select the next available channel) and only want one
voice port to ring on an incoming call.
ã 1999 Consumer Microcircuits Limited
ã 1999 Chiron Technology Limited
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D/228/1
CMLMICRO [ CML MICROCIRCUITS ]
