HP LaserJet 4 Service Manual - Page 70

Pacing (Handshaking) Pacing (or "handshaking") is a type of communication between the printer and the computer. This is an important item in the printer because it allows the printer to tell the computer when to send information. If the printer is unable to receive information, for example, when the print buffer is full or when the printer is out of paper, a signal is sent to the computer to stop sending information. When the printer is able to resume receiving information, it sends another signal to the computer to send more data. Pacing is set through the control panel's Serial Menu. Two types of handshaking are supported by your printer: • Select DTR/DSR through the Serial Menu's PACING item if the computer requires hardware flow control (most personal computers do). Through the Serial Menu's DTR POLARITY item, the DTR polarity can be set to High or Low. The default is DTR POLARITY=HI • Select XON/XOFF through the Serial Menu's PACING item if the computer requires software flow control (for example, if you are using a UNIX workstation). Note that status readback messages are not paced when XON/XOFF is selected. Through the Serial Menu's ROBUST XON item, Robust Xon can be set to ON (the default) or OFF. Note that the ROBUST XON item only appears under the Serial Menu if XON/XOFF was selected. 3-34 Configuration