c. Line Hammer Decoder Boards (LHD/1). The two line hammer decoder boards (LHD/1) in the bustle are
identical and interchangeable. Each board controls hammer firing of all odd hammers or all even hammers depending on
which bustle slot the board is inserted.
d. Power Supply Regulator Board (PSR/1). The power supply regulator board (PSR/1) in the bustle receives
raw, unregulated dc voltages from the rectifiers on the power control board (XPS/3). The PSR board has five functions.
(1) It regulates the four low voltage (+15, +5, -15, and -12 volt) power supplies.
(2) Its crowbar circuit turns off the high voltage supply in case of overcurrent detection.
(3) It regulates the high voltage +157 volts unregulated dc power from the XPS/3 board. The output of the
high voltage regulator is 109 V.
(4) Its protection circuits sense for high or low voltage conditions.
(5) Its photoelectric sensing circuits pick up and amplify signals from the type finger photo transistors.
e. Logic Board (LOG/8). The logic board (LOG/8) contains the circuitry associated with processing data from
the unbuffered parallel interface board (CINT/2) to the line printer print mechanism. It also contains the paper handling
logic, the motor control logic, the alarm logic and clocking and timing for print synchronization.
(1) Paper handling logic works in conjunction with the vertical format unit photosensor board (TVFC/1)
housed in the slew strobe assembly.
(2) Motor control logic is activated when it receives a motor-on or motor-off command from the data source.
(3) Alarm logic is activated when the line printer is out of paper, when there is a slow speed on the print belt,
or when there is a low voltage on any of the power supplies on the PSR.
(4) Clocking and timing for print synchronization is based on a 2-phase clock system derived from a 3.2
MHz crystal clock oscillator. The two Pico fuses (fig. 2-13) protect the clock timing circuits.