Fluke Biomedical 945A - Manual (Page 62)

Option Board Bus
The option board bus is available on connector J3. All address, data, and control signals are provided to
allow various digital/analog circuit boards to directly interface to the main circuit board. Decoded signals
for asynchronous communications interface adapter option, and the general purpose interface bus option
are available on the option board interface connector.
Relay Circuit Board
The relay circuit board contains four independently controlled mechanical relays. Each relay provides
two Form C sets of contacts with the exception of the check source and alarm relays which provide a
single Form C set of contacts. Interconnection is from J2 on the relay board to J2 on the main circuit
board. The control signals (active low) and + 15 volts common are provided. The relays typically perform
the following functions:
K1 Spare - Normally not controlled by std. 946A
K2: Check Source
K3: Fail
K4: Warn
K5: Alarm
The relay contacts are provided to the user via rear panel connector P1. See specifications for contact
ratings. Varistors (V1-V16) provide transient protection across the contacts.
Front Panel Circuit Board
The front panel circuit board consists of the 7 segment display, backlights, status indicators, switches,
and bargraph assembly. The front panel interfaces to the main circuit board via interconnecting row 100,
200, and 300. The main power switch also mounts to the front panel circuit board. Refer to figure 4-5 for
a view of the front panel.
Circuit Description (Front Panel Circuit Board)
The 7 segment displays are controlled by the display controller as described in "Display Control". The
bargraph is controlled by the circuitry described in "Bargraph (Write Only)". The status indicators are
described in "Status Indicators (Write Only)". Switches are described in "Switch Inputs".
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