AVIATION RECORDERS
OPERATOR'S MANUAL
MODEL FA2100GSE
PORTABLE INTERFACE (PI)
CVR Operation
Rev. 01 Page 3
−
7
May 01/99
3.4.4
Rotor Speed FSK Data
Rotor Speed output data is displayed (in Hz) on the following PI menus:
D
Playback Menu
D
File Playback Menu
D
Can be selected for display from the Special Functions Menu.
Rotor Speed FSK data is output by the PI each time a new rotor speed value is available. The
bit rate is 768 bit/sec
5% with the LSB transmitted first. The Rotor Speed FSK level is
2 vrms
−
122 vrms, differential input.
A “1” bit is represented by a frequency of 4193
30 Hz.
A “0” bit is represented by a frequency of 3607
30 Hz.
To ensure synchronization by ground based equipment, the input label (Bits 1
−
8) are set to “0”
and Bit 9 is set to “1”. Bits 10
−
12 are set to “0”. Bits 13
−
20 represent the reference count and
bits 21
−
32 represent the rotor pulse count. These counts are output as presented by the
FA2100 over the GSE TDM bus, words 24 and 25. The output signal has an output imped-
ance of 20 ohms maximum and a signal level of 2.45 vrms +10% across a load impedance of
600 ohms.
/TC_INH
(enable)
TC
32 / 768 Sec
32 bits of data (1 bit = 1 / 768 Sec)
.
.
.
FSK
.
.
.
ONCE EVERY FOUR (4) SECONDS
Mark (1) = 4193 + 30Hz
Space (0) = 3607 + 30Hz
Figure 3
−
3.
GMT FSK And Rotor Speed FSK 32
−
bit Format
Rotor Pulse Frequency = (400 Hz) x (Rotor Pulse Count) / (Reference Count), or Rotor
Pulse Frequency = 400 x Word 2 / Word 1.
For displaying rotor speed the user must be able to select the display to be frequency or cal-
culated revolutions per minute (RPM). To allow the conversion from frequency to RPM the
user must provide a matching frequency to RPM ratio. For example, 6 kHz = 300 RPM. To
determine the calculated RPM use the following formula:
RPM = Rotor Pulse Frequency x (Rotor RPM/Tach Frequency).
Rev. 04 Page 3
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7
Jun. 15/05