HP 5961-0509 manual Echo Command, Echo command followed by a Free Space command. The printer

Echo Command

The Echo command echoes its value field (in ASCII format) back to the host.

EC * s # X

#=Echo value (ASCII)

Default	=	0
Range	=	–32767 to 32767

If multiple users are requesting status, it can be difficult to distinguish one user’s status response from another. The Echo command provides the means to label status responses. Since the user-selected value for the value field is returned, this command can be used as a user identification mark or “place holder.” Sending the Echo command, with a specific user-selected value,

at the beginning of a status request enables users to identify their status response data.

Notes	Status readback requests are processed in the order they are
	received.
	Status readback responses are returned to the printer port from
	which they were received.
	When selecting an echo value, it is important to select a number
	which is not likely to be used by another user, such as a random
	number.
	This example illustrates why using the Echo command with a random
	number is important. Assume an application uses a fixed number
	each time the Echo command is sent. Further, assume the printer
	running the application was turned off after the application sent the
	Echo command followed by a Free Space command. The printer
	generates the status readback responses to the Echo command and
	Free Space commands. Since the host is not accepting data, the data
	will be in the printer waiting for the host to accept it. Now, assume the
	host computer is turned on and the application is again executed.

EN Echo Command 16-25