Display Board
Principles of Operation
Force EZ-C Series Service Manual
5-15
REM Switch Circuit
The REM switch circuit detects the presence of a REM patient return electrode
plugged into the Patient Return Electrode receptacle. The center plastic pin on the
REM plug moves a mechanical lever in the receptacle, allowing it to sense the
plug and open S9. This allows R55 to pull REM_SW high, telling the main
microcontroller that a REM patient return electrode is connected to the generator.
When you use an electrode without the REM safety feature, S9 remains closed
and REM_SW is pulled low. Capacitor C23 filters noise on REM_SW. Resistor
R56 limits the amount of current that flows through S9 when it closes and C23
discharges.
Front Panel Footswitch Circuit
The footswitch circuit on the Display board provides a means of activating the
selected receptacle: the Bipolar Instrument receptacle or the single-pin Accessory
Instrument receptacle. This circuit consists of a footswitch receptacle, an isolated
DC/DC converter, two optoisolators, and associated circuitry.
The footswitch connector (P1) provides the connecting point for the footswitch.
The common mode choke (L1) and capacitors (C1–C3, C16–C18, and C24–C26)
provide filtering that blocks high frequency noise from exiting the generator on
the footswitch cable. Note that C16–C18 decouple the footswitch outputs to
DGND and then C1–C3 and C24–C26 decouple DGND to CHGND. This occurs
in two stages in order to use the DGND plane on the board as a low impedance
path from the footswitch circuit to the edge of the board, where it is easier to
connect to chassis ground.
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Pressing a footswitch coag pedal allows, +V_ISO_5_FIL, pulling
MON1_COAG\ low through U1, to pull the corresponding signal
(FRONT_FSW_COAG_FIL) high.
•
Pressing a footswitch cut pedal V_ISO_5_FIL, pulling MON1_CUT\
low through U2, to pull the corresponding signal (FRONT_FSW_CUT_FIL)
high.
Resistors R5 and R6 set the amount of current flowing through optoisolators U1
and U2. An isolated DC/DC converter (U3) provides the power source for the
footswitch circuit via isolated power (+V_ISO_5) and ground (ISO5). Capacitors
C6, C10, and C15 provide high frequency filtering to reduce emissions. Capacitor
C12 supplies a source for current spikes flowing into the switching input of U3.
