Garmin GTN 725, Installation Manual

Page: 76 / 178

Page 4-28 GTN 725/750 TSO Installation Manual
Rev. A 190-01007-02
4.3.17 DME Tuning (GTN 750 only)
4.3.17.1 DME Tuning Function
The GTN 750 can channel a DME based on the tuned VLOC frequency. The GTN 750 outputs 2 of 5,
BCD, or Slip parallel DME and King Serial DME channeling format. When DME COMMON is held
low, the GTN 750 actively tunes the DME.
4.3.17.2 DME Tuning Electrical Characteristics
4.3.17.2.1 Parallel DME Tuning
Pin Name Connector Pin I/O
PAR DME 100KHZ-A/NAV SERIAL DME HOLD P1004 37 Out
PAR DME 100KHZ-B P1004 39 Out
PAR DME 100KHZ-C P1004 40 Out
PAR DME 100KHZ-D P1004 42 Out
PAR DME 100KHZ-E P1004 54 Out
PAR DME 50KHZ P1004 43 Out
PAR DME 1MHZ-A P1004 45 Out
PAR DME 1MHZ-B P1004 46 Out
PAR DME 1MHZ-C P1004 47 Out
PAR DME 1MHZ-D/NAV SERIAL DME ON P1004 33 Out
PAR DME 1 MHZ-E P1004 56 Out
DME COMMON P1004 41 In
For each of the parallel DME tuning discrete outputs, the driver output voltage is not more than 1.0 V
while sinking 20 mA. The maximum off state leakage current with respect to ground is less than 10
μ
A.
DME COMMON must be pulled low to indicate to the GTN 750 that it is the device channeling the DME.
DME COMMON is considered active if either the voltage to ground is <1.9 V or the resistance to ground
is <375
Ω
. These inputs are considered inactive if the voltage to ground is 11-33 VDC.
4.3.17.2.2 King Serial DME Tuning
Pin Name Connector Pin I/O
SERIAL DME – DATA P1004 19 Out
SERIAL DME – CLOCK P1004 18 Out
SERIAL DME- RNAV/CH REQ P1004 20 In
SERIAL DME - RNAV MODE P1004 21 In
DME COMMON P1004 41 In
SERIAL DME – DME REQUEST P1004 44 I/O
When SERIAL DME – DATA or SERIAL DME – CLOCK is asserted high and driving a 360
Ω
load, the
driver output voltage is not less than 8 V, and when asserted low is not greater than 10 mV.
SERIAL DME – RNAV/CH REQ, SER DME – RNAV MODE, and DME COMMON are considered
active if either the voltage to ground is <1.9 V or the resistance to ground is <375
Ω
. These inputs are
considered inactive if the voltage to ground is 11-33 VDC.
DME COMMON must be pulled low to indicate to the GTN 650/750 that it is the device channeling the
DME.