Respironics Trilogy 02, Technical Information

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P
AGE
4-11
T
RILOGY
S
ERVICE
& T
ECHNICAL
I
NFORMATION
1002735, V
ER
. 05
4.6 F
RONT
P
ANEL
B
OARD
The front panel board provides the user interface support in the Trilogy ventilator. It includes circuitry for the
keypad, keypad backlight, audible alarm, visual alarm, and AC present indicator.
F
IGURE
4-6 F
RONT
P
ANEL
I
NTERFACE
B
OARD
B
LOCK
D
IAGRAM
.
AC Power LED – A green LED (CR3) indicates the presence of AC/DC supply to the Trilogy ventilator.
Red LED – Two red LED’s (CR2 & CR19) are used to indicate urgent and high priority alarm conditions. They
are driven by two separate control lines from the CPU and the CPLD for redundancy during power fail
conditions. Compared to normal operation, during power fail the red LED’s have lower luminous intensity
achieved using current limiting resistors (R105, R106) to preserve power consumption.
Yellow LED – Two yellow LED’s (CR4 & CR5) are used to indicate low priority alarm conditions.
Keypad / User Input Switch Circuit – The front panel has 6 four-legged metal dimple types dome switches
for user input. They support alarm silence, start/stop, left, right, up, and down functions. All share active low
signal configuration. They are powered by the 3.3V power supply with the exception of the start/stop and right
function keys which use the 3.3V_PLD to support additional function during the power fail and low power
mode.
Keypad Backlight - An array of 12 white LED’s (CR7 to CR18) are used to provide back light for the keypad.
All the while LED’s are controlled by a common switch (Q2).
Audible Alarm Signal - Each speaker has a mono-tone and a multi-tone audio alarm signal source. The mono
tone audio alarm signal is generated by the low power oscillators (U3 & U5) running at a fixed frequency of 2.9
KHz. This frequency is set using external resistors (R12 & 14). The multi-tone audio alarm signal is generated
using a combination of four harmonic signals. The 4-bit binary counter (U6) receives a square wave signal at
various frequencies to generate these four harmonic signals. Each of the four harmonics signals is wave
shaped using high-pass (RC) filters and low-pass (active) filter (U1). A summing amplifier (U2) then adds the
Quad
Counter
Filter
2:1
mux
Low Power
Oscillator
#1 +
Speaker
Driver
#1
Monitor
Circuit
#1
Speaker
Driver
#2
Monitor
Circuit
#2
+
Red LED Yellow LED
Keypad
Backlight
AC Power
LED
Keypad
Power Mux
#1
Power Mux
#2
Low Power
Oscillator
#2
+
Speaker
#1
Power
Speaker
#2
Power
To
System
Board