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Appendix D - V.25bis Operation
Dial Phone Number Provided (CRN) Command
The CRN command permits the dialing of the phone number immediately following it (from the
command line). It is similar to the
D
command of the AT command set, except that the number is first
checked against the Delayed Number and Forbidden Number list. If permitted, depending on the
country regulations in effect, the number will then be dialed. For example, if you enter
CRN7859875
and hit RETURN, your modem will check the two lists. If the number is on the Delayed Numbers list,
you can dial that number again after
t
minutes have passed. If the number is on the Forbidden list, a
CFIFC
message will be displayed.
You can use various commands from the AT command set within the CRN command line to facilitate
the dialing process, such as
P
,
T
, or
:
for pulse dialing, tone dialing and wait for dial tone. V.25
bis
supports
“smart”
dialing.
To dial a phone number, enter
CRNdd...dd
where
dd...dd
is the phone number, which can be up to
20 characters long using any character on the telephone pad (0 through 9, *, #, P, T, and :).
Some additional dialing characters may be available, based on country regulations.
Listing Delayed Phone Numbers (RLD) Command
When a phone number is dialed by a CRN command and a connection is not made, the number is
entered in the modem's V.25
bis
Delayed Number list along with the number of retry attempts. Any
further dialing attempts will be delayed some amount of time (determined by the regulations of each
country). While the delay is in progress, the modem will give a DLC indication. The list contains eight
numbers. When filled, the next number failing
“bumps”
off the oldest number on the list onto the
Forbidden Number list. Numbers on the Delayed Number list that succeed in a connect attempt are
removed. If a certain number of failed attempts occur (the number of failed attempts is specified by
each country), the number is entered into the V.25
bis
Forbidden Phone Number List. Forbidden
phone numbers cannot be dialed at all. To list the phone numbers on the V.25
bis
Delayed Phone
Number List, enter
RLD
and hit RETURN.
Listing Forbidden Phone Number (RLF) Command
Those phone numbers that have failed to connect the required number of times as specified by
country regulations are removed from the Delayed Number list and entered onto the V.25
bis
Forbidden Number list. Numbers on the Forbidden Number list cannot be dialed at all for some
maximum amount of time, which is also specified by country regulations. In some countries, the time
might be one hour, and in others the number may never be dialed again. The forbidden list is eight
numbers long, with the newest number replacing the oldest if the memory is full. To list the numbers
in the Forbidden list enter
RLF
and hit RETURN.
Disregard or Connect to Incoming Calls (DIC or CIC) Command
The Disregard or Connect to Incoming Calls commands are used for Auto-Answer operations.
Depending on the country regulations, your modem will wait some amount of time or number of rings
before answering the call. During that time, you can stop the modem from answering the call by
entering the
DIC
(Disregard Incoming Calls) command.
CIC
(Connect to Incoming Calls) command
will cause your modem to answer the call (either reversing the effect of a DIC command or simply
have your modem answer the call immediately without waiting the regulation time before answering).