; return to local command state
This modifier orders the modem to return to local command state — without disconnecting — after it has dialed the number.
You may use this modifier to communicate with a mainframe computer using security callback. Your modem dials the number of the mainframe computer and then immediately returns to local command state. Another ATD command can then be used to generate the tones required for the callback identity number.
The ; used in conjunction with the M2 command, allows you to return to local command state with the speaker turned on, allowing you to monitor the progress of the call at the remote modem.
R reverse mode
This modifier enables you to switch to answer mode after dialling. When connecting to another modem, one modem must be in originate mode and the other in answer mode to establish a connection. When you use a dial command, your modem is normally in the originate mode.
The R dial modifier enables you to connect to originate only modems. This is also useful when you want to send information at 1200/75 bps (CCITT V.23 standard communications).
If you communicate with another computer in originate mode at 1200/75 bps, you will be sending data at 75 bps and receiving at 1200 bps. If you have a lot of information to send and not much to receive, it makes sense to switch to answer mode, so that you are sending at the faster rate.
For example:
To dial the number
•Type: ATD9999876R <E>
@ wait for quiet answer
The @ modifier orders the modem to wait for one or more rings within the time specified by S Register 7, followed by a period of five seconds of silence occuring some time before dialling the remaining numbers in a phone number.
The default value of S Register 7 is 30. Using this default, the modem will dial the first number, listen for a period of five seconds silence during the next 30 seconds and then, if the silence is detected, dial the next part of the number.
If five seconds of continuous silence is not detected, the modem will hang up and return a message: NO ANSWER If the phone number is engaged, the modem will return a message: BUSY This modifier is useful for remote access databases which require an identification code to be tone dialed before those databases generate an answer tone.
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