Philips FM-2, Service Manual

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Mechanical Description
Chapter 1 - General Information 9
with the monitor, please see “Parallel I/O Communications Interface” on
page 18.
For further details of the pinouts and the cable specifications, see
Chapter 2, “System Interfaces”.
Keypad and Navigation Wheel
There are seven front-panel switches, two LEDs, and one wheel push-button
switch. All of these buttons go to the main-board except for the ON/OFF push
button, which goes directly to the power supply. The software monitors these
signals to determine which buttons were pushed. The two LEDs are located on
the control panel and inform the user of mains or battery operation.
The wheel consists of a mechanical rotary encoder wheel with a momentary
push button switch. As the knob is rotated, quadrature-coded outputs are
generated. The phase relationship between the two signals, in quadrature, reflect
the clockwise or counter clockwise rotation of the wheel. This relationship is
translated to move the cursor on the LCD display forward or backward,
depending on which way the wheel is rotated.
Power Supplies
The unit is operated from a 6-volt 4 AH sealed lead acid battery. The power
supply provides enough power to charge the battery even when the unit is
operating.
The monitor power is controlled by alternate button closures of the front panel
membrane switch. Unit operation starts only via a push of the front panel
button, but operation will stop after a delay of a few seconds when pushing the
front-panel membrane switch. This delay permits the main-board processor to
shut down in an orderly fashion, after storing the parameters and data, if any.