Unit installation

5-3

The controller has a table which it uses to keep track of the information for each command. This

information is used when the controller tries to find out what command you have entered the name

for. If more than one command have the same name, it can also be used to intelligently figure out

which one you wanted. Some of the entries are:

Command name (including the length of the name).

Data length: that is how many digits, if any, are needed after the command name.

If the data length is not zero, whether the amount must be exact or whether more digits can be

entered.

DTMF execution mask (see command 130)

User level required to execute (see Chapter 18)

For example, Command 009 would have a data length of zero, command 000 would have a data

length of 2 which must be exact, and command 036 would have a minimum data length of 3, but

could be longer. Other checking such as making sure that the data for 036 is a multiple of three

digits and limiting the maximum length is done by the commands themselves. Where the checking

is done is important. The checks that can be done with the information in the table can be used to

help figure out which command you want to execute when the names are ambiguous, while the

checks that are done within the commands themselves are too late.

When you enter a command and unkey or press enter, the controller scans the whole table of

commands looking for a match. It ignores any commands that would be blocked by the DTMF

execution mask or that require that you log on using a password to execute. It also ignores any

that it knows have the wrong number of data digits after the command name (using the information

in the table as discussed above), although there are some cases where it can't tell until the command

is chosen and causes an error. From the remaining commands, it chooses the one with the longest

name that matches what was entered. In case of a tie, it chooses the one with the lowest command

number.

For example, if you have commands named "1", "12", "123", "1234" and "12345" and you enter

"12399", assuming that all of them pass the initial execution mask and password and data length

checks, the controller will select the command named "123" and will execute it with the data digits

"99". That is it will find the longest match, then use the rest of the digits as data. Keep this in mind

when you change command names to be less than three digits. If you change the "Retrieve Public

Mail" command (177) to have the name "12", then enter "123" to get the mail from mailbox 3, you

may instead execute command "123" because it also matches and has a longer name. If command

123 needs additional digits after the command name, the controller will figure out what you mean,

but sometimes it just can't tell. So when you rename commands, keep in mind that any name that is

the same as the beginning of another name might be ambiguous.

This ability of the controller to find the longest matching name can be used in several practical

ways. For example, command 000 connects two ports together. It normally sends "X connect Y"

as the voice response. If you have a repeater on port 1 and a link to another site on port 2, you

might want the message to be "Link up" instead. You could make a macro named "00012" or

"00021" that would connect the two ports and send that message. Then entering "00012" or

"00021" would cause your custom message to be sent, while "00013" or any other command

starting with "000" would access the normal command 000 and cause the normal "X connect Y"