Honeywell BENDIX/KING KAP 140 Maintenance Manual page 85

4.3.11 RS232 INTERFACE TO THE KC 140
PIN
P1401 -- 28
P1401 -- 29
The RS232 interface consists of two signal lines: RXD_RS232 (receive), and TXD_RS232
(transmit). The KC 140 uses this interface to talk to the personal computer (PC) or laptop computer.
This interface allows the KC 140 flight computer to transmit error codes, save installation
parameters, and enter the diagnostic pages. For more information on using the RS 232 interface
with the KAP 140, see the Remote Terminal Interface section.
The RS232 receiver in the KC 140 is typically biased at --10V (without PC keyboard activity). When
a key is pressed on the PC keyboard, the signal line transmits a series of short pulses (the high
side of the pulse is around +12V). The RS232 transmitter in the KC 140 is typically biased at --8.5V
when it is not transmitting information to the PC. When the KC 140 is sending information to the
PC, the signal line transmits a series of short pulse (the high side of the pulse is around +8.5V).
4.3.12 AUDIO PANEL INTERFACE TO THE KC 140
PIN
P1401 -- 6
P1402 -- 38
P1402 -- 49
The MIDDLE_MARKER output of the audio panel is used by the KC 140 to determine gains to use
when tracking glideslope and localizer. When the middle marker becomes active, the gain
decreases. If the voltage is above 2.5V, the middle marker input is considered active. If the voltage
is below 1.5V, the middle marker input is considered inactive. The state of the middle marker input
is displayed on the DISCRETE INPUT STRAPS/VALIDS diagnostic page.
The AUDIO_ALERT output is a transformer isolated output with a series 500 ohm resistor. This
output provides a 2KHz sine wave whenever the AP mode is disengaged. The amplitude of this
output can be set in the installation pages or on the DISCRETE OUTPUTS diagnostic page.
Generation of the aural alert can also be done via the DISCRETE OUTPUTS diagnostic page.
The amplitude of the sine wave should be somewhere between 4.5 Vrms to 0.3 Vrms (assuming
a 500 ohm load), depending upon the volume level setting. There is a 243 ohm load
(AUDIO_LOAD) to ground in the KC 140 that can be jumpered to the AUDIO_ALERT output to
decrease the maximum volume level. The AUDIO_ALERT output also provides the KC 140 voice
messaging signal, if that option has been selected in the installation options.
NOTE: When the AP mode is engaged and power to the unit is lost, the audio output provides a
2KHz tone. Under this condition, the volume of the tone is set to maximum, not the level that is
set in diagnostics mode.
Revision 2, Dec/2002
CS:15574F02.IDU
BENDIX/KING
KAP 140
DESCRIPTION
TXD_RS232
RXD_RS232
DESCRIPTION
AUDIO_ALERT
MIDDLE_MARKER
AUDIO_LOAD
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