Eicon Networks DIVA T/A ISDN Modem For more details, refer to the Rvscom documentation, AT!X56=n

ISDN Configuration Commands

AT!On	Outgoing Call Type. Specifies the default call type for outgoing calls when a user
	enters an ATD command without a special modifier. Use of a modifier overrides this
	parameter.
	n=0	Data call using protocol set in AT%A2=n (default).
	n=3	Data over voice bearer capability call (North America only)
	n=4	Transparent over voice (Audio) (reserved for RVSCOM).
	n=5	Transparent over voice (speech) (reserved for RVSCOM).
	The n=4 and n=5 options (transparent over voice) send and receive voice data
	unmodified to and from the ISDN B channel and the DIVA T/A. When no data is being
	transferred, the protocol fills the outgoing ISDN line with ‘voice silence’ bit patterns.
	For more details, refer to the RVSCOM documentation.
AT!X56=n	Delay between 64K data call failure and 56K data call attempt. If a 64K data call
	fails due to network congestion or if a service or option was not available or not
	implemented, a 56K data connection is automatically attempted. This command
	specifies the delay, in seconds, before the 56K attempt is made.
	Values: 0-10 (wait n seconds before retry); 254 (use pre-configured values depending
	on region); 255 (do not attempt 56k data call retry).
	Default: Australia & Japan, no retry (n=255); all other regions, immediate retry (n=254).

DIVA T/A ISDN Modem Reference Guide ◆ Page 35