One value can be set for the LPR Print Monitor, in the following registry path:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Print\ Monitors\LPR Port\Ports\<portname>\Timeouts
PrintSwitch REG_SZ Control character string
Specifies the format control character that the LPR Print Monitor should send to the print server via the control file. By default, this parameter doesn't exist in the registry, and "l" (lowercase L) is sent as the control character. You can set it to any string. If set, the first character of the string is taken as the format control character and sent to the print server. The rest of the string is ignored. In situations, you may need to use "f" instead of "l".
Default: (none)