Does the model of modem used in the MultiAccess ACS support distinctive ring?

Yes it does, by reporting the duration of the ring on and ring off intervals of the incoming ring signal. The internal modem is the MT5634SMI-V92 Global socket modem and the AT command that enables this functionality is +vdr=x,y.

To utilize this feature, your application would have to be accessing the modem via the Modem Sharing functionality of the ACS and the telephone line connected to the ACS would have to be provisioned with a distinctive ring service and multiple telephone numbers. Each telephone number would have a unique ring pattern (cadence). The modem's auto answer capability should be disabled (set s0=0) when distinctive ring reporting is enabled. This allows the host application to control if or how the modem answers. This feature (+vdr) is not applicable when the RAS functionality of the MultiAccess is being utilized.

For Example:

If you are developing a host application that is to receive serial data from various types of remote sites, and you want the host application to automatically adjust itself based on the type of client that is calling in, then it may be advantageous to utilize the modem's distinctive ring feature as a means of identifying the type of client. The client would dial the telephone number you associate with each application. Your host application would have to be designed to look for certain ring patterns (as described below), run the appropriate application and then instruct the modem to answer appropriately.

Another Example:

If the ACS device is on a phone line that is shared with other devices (Fax machine, Answering Machine, etc), when a certain ring cadence is reported, have your application instruct the modem to answer. Ignore any other ring pattern so that the other device(s) can handle the call.

Command: +VDR=x, y Distinctive Ring Report

Values: x = 0, 1 Distinctive Ring report control. See description.
y = 0-255 Minimum ring interval in 100 ms units. See description.

Default: 0, 0

Description: Enables reporting of ring cadence information to the DTE and specifies the minimum ring cadence that will be reported. The report format is one line per silence period and one line per ring period. The length of the silence period is in the form DROF=number in units of 100 ms<CR><LF>, and the length of the ring is in the form DRON=number in units of 100 ms<CR><LF>. The modem may produce a Ring event code after the DRON message if enabled by the y parameter. The y parameter must be set to a value equal to or smaller than the expected ring cadence in order to pass the report to the DTE.

+VDR=0, N/A Disables Distinctive Ring cadence reporting.
+VDR=1, 0 Enables Distinctive Ring cadence reporting. Other call progress result codes (including RING) are reported as normal.
+VDR=1,>0 Enables Distinctive Ring cadence reporting. The RING result code is reported after the falling edge of the ring pulse (i.e., after the DRON report).
+VDR=? Displays the allowed values.
+VDR? Displays the current value.