USRobotics V.34 user manual DTE is the source of the Transmit clock timing

COURIER HIGH SPEED MODEMS

	&X1	The DTE is the source of the Transmit clock timing
		signals and sends them to the Courier over the RS-232
		interface. This setting is used typically in leased line
		multiplexed operations. (Multiplexors divide the phone
		channel so that the channel carries several calls at the
		same time.)
		The DTE ignores the Courier's clock timing signals and
		negotiates the DTE and connection rates.
	&X2	The Courier's Receiver clock is the source of the timing
		signals. The signals are looped to the Transmit clock and
		sent to your DTE over the RS-232 interface. This setting
		is only used in those systems that require
		synchronization of data flowing in both directions.
&Yn	Break handling. This command allows you to send a break to
	abort data transfer without disconnecting from the phone link.
	&Y0	Destructive, don't send Break.
	&Y1	Destructive, expedited (Default).
	&Y2	Nondestructive, expedited.
	&Y3	Nondestructive, unexpedited; modem sends Break in
		sequence with data received from computer or terminal.
&ZC?	Display the stored command string.

&ZC=s Write the following command string s to NVRAM. The command string may be up to 40 characters long; spaces are not counted. This command can be used so that you can call another modem without loading your communications software.

After storing a command, you can program the voice/data switch to execute the stored command string when pressed. The following example assigns a command string that displays the link diagnostics screen when you press the voice/data switch.

AT&ZC=I6 <Enter>

C-16 Alphabetical Command Summary