Multi-Tech Systems BA-Series manual Dial Modifier Commands, DTR Dialing $D, Voice/Data Dialing $VD

MultiModemBA User Guide

DTR Dialing $D

An alternate method of causing the modem to automatically dial is DTR Dialing. Data Terminal Ready (DTR) is a signal that comes into the modem from the terminal or computer to which it is connected, on pin 20 of the RS-232C interface. In DTR dialing, the modem automatically dials a stored number as soon as it receives a high DTR Signal. The DTR dialing method is popular in synchronous applications.

To activate DTR Dialing, enter AT$D1 and hit RETURN. The modem dials the phone number stored in the N0 location of memory when it receives a high DTR signal. DTR must remain high for the duration of the call, until disconnect. To deactivate DTR dialing, enter AT$D0 and hit RETURN.

Note when using DTR Dialing in a synchronous application, be sure DIP-Switch #8 is in the UP position to disable V.25bis Command mode.

Voice/Data Dialing $VD

Another alternate method of causing the modem to automatically dial is Voice/Data Dialing. With Voice/Data Dialing, the modem automatically dials the phone number stored in the N1 position of memory whenever the Voice/Data switch is toggled. You must first enter AT$VD1&W0<CR>. This command string enables Voice/Data dialing when the Voice/Data toggle switch is activated. To disable Voice/Data Dialing (default), enter the command AT$VD0 W0<CR>.

4.4.2Dial Modifier Commands

There are several command characters that can be included within a dialing command (following the letter D), called “Dial Modifiers”. They have various functions, including the selection of Pulse or Tone Dialing, pauses in the dial sequence, automatic re-dials if a number is busy, and reverting to the Command mode or switching to the Answer mode after dialing.

Pulse or Tone Dial P T

The modem dials numbers using either pulse or tone dialing, or a combination of both methods. Pulse dialing is a method used by rotary-dial telephones, which involves the timed opening and closing of line relay.

Tone dialing is the method used by push-button (touch tone) telephones, and is sometimes referred to as DTMF, or Dual-Tone Multi-Frequency dialing.

The method used is selected by including a P for Pulse or a T for Tone in the dialing command, right before the digits you wish to have dialed in that manner.

For example, you would pulse-dial the number 555-1212 by entering ATDP5551212 and hitting RETURN. You could tone-dial the same number by entering ATDT5551212 and hitting RETURN. If neither Pulse nor Tone dialing is specified in the dial command, the modem uses whatever method used last. If the modem has been reset or just powered up, it uses Pulse dialing, even if the letter P is not included in your dial command.

Nearly all telephone systems in the U.S. are now compatible with tone dialing. Since that is the faster method, you will probably choose the tone method for your dialing.

An example of combining pulse and tone dialing could involve a PBX system where 9 had to be pulse-dialed first, then the rest of the number tone-dialed after pausing for a second dial tone. The number would be dialed by entering ATDP9, T5551212 and RETURN. (The comma causes a pause, which we’ll explain soon.)

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