HP 4600 Service Manual - Page 178

Cassette detection and cassette paper-size detection The printer can sense whether the cassette (tray 2, tray3/tray 4) is installed correctly, and it can sense the size of the paper in the cassette. Paper-size detection switches at the back of the cassette send this information to the DC controller. The DC controller determines which size is loaded by reading various switches. See Table 5-6 Cassette paper-size detection. Figure 5-35 Cassette papersize detection switches shows how the switches are stacked. Table 5-6 Cassette paper-size detection Paper size A4 B5 A5 Letter Legal Executive Custom No cassette Paper-size detection switch SW1 SW2 on off on on on off off on off off off on on on off off SW3 off off on on on off on off Although the cassette determines the paper size by reading the switches, it is possible that the user can select a different size from what is loaded, creating an error in paper-size detection. The paper leading-edge sensor detects when the leading edge and the trailing edge of a sheet pass it. By measuring the time between the passing of the leading edge and trailing edge, the sensor can determine the actual size of the sheet. If this measured size differs from the size specified by the formatter or the switch combination, the DC controller determines a mismatch. The sheet is ejected from the printer, and the printer stops. Figure 5-35 Cassette paper-size detection switches 162 Chapter 5 Theory of operation ENWW