Garmin GNS 480, Installation Manaul

Page: 71 / 200

Installation Procedures
GNS 480 (CNX80) Installation Manual 560-0982-01 Rev L 2-39
2.8.11 Time Mark Output
P1-17 Time Mark Out -
P1-19 Time Mark Out +
The Time Mark Out is a differential output that provides a 1 msec pulse once each second. This time
reference is derived from GPS satellites.
2.8.12 VHF COM
The GNS 480 provides an internal COM transceiver that can be interfaced to an audio panel or connected
directly to a speaker. The PTT input is used to enable the COM MIC audio and cause the COM
transceiver to transmit on the active frequency. Optional external inputs are available to allow the user to
toggle the active and standby COM frequencies, and select COM frequencies from a user-defined
frequency list.
Refer to Appendix D for interconnect information.
Refer to section 3.2.1.5 for information on setting the RF squelch and mic gain values.
2.8.12.1 COM Headphone and Speaker Audio Out
P4-14 COM Headphone Out
P4-6 COM Speaker Out
P4-13 COM Audio Ground
The COM Headphone Out is a low-level audio output that is intended to drive a headset or audio panel.
This output will provide 280 mW into a 100
Ω
load, or 120 mW into a 500
Ω
load.
The COM Speaker Out is a high-level audio output that is available to drive a speaker. This output will
provide 12 watts into a 4
Ω
load, or 8 watts into an 8
Ω
load.
Both the Headphone and Speaker outputs use the same COM Audio Ground. For normal installations, it is
recommended that the Headphone output be used, and the COM Speaker output be left unconnected.
2.8.12.2 COM MIC Audio In
P4-8 COM MIC In High
P4-7 COM MIC In Low
The COM MIC input is designed for a standard carbon or dynamic mic with integrated pre-amp providing
minimum 70 mv rms into 1000
Ω
load. The GNS 480 provides a bias voltage to the microphone.
2.8.12.3 Push to Talk (PTT)
P4-4 PTT
The PTT is used to enable the COM MIC audio and cause the COM transceiver to transmit on the active
frequency. Refer to section 2.8.9.4 for additional details.
2.8.12.4 COM Flip-Flop Switch
P1-14 COM Flip Flop In
The COM Flip-Flop In can be used to toggle the active and standby COM frequencies. Refer to section
2.8.9.2 for additional details.