Click the Rumba Printer Session icon. Select Options / Character Translation / Configure / Custom / OK. Select the escape character (value of 1B) on the ASCII side and then select the EBICD character you want to use for the escape character. The "Generic/Text only" printer driver should be used so that the escape character will not be stripped off by the printer driver. The HP LJ 4 or other printer driver may be used if it does not strip the escape character, but the printer driver will insert its own PCL commands which may interfere with the commands you send.
In your application print <esc>&f(form number)y4X to the printer to select (form number), where <esc> is the character you selected in Rumba to be translated into the escape character in ASCII.