Transmit Audio Routing To Remote; Transmit Indication - Motorola APX 7500 Detailed Service Manual

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other means to set the HLGT to audio ratio. If "TRC AGC Configuration" is disabled, or "Hardware
PTT" or "ACIM" are selected as the "Wireline Function" in the Consolette Configuration Audio
Parameters page, then the gain of the wireline transmit audio is adjustable linearly via the "Wireline
In (TX) Gain Setting". This gain setting can be used to compensate for a line level other than 0 dBm.
Note: This setting is disabled when wireline AGC is enabled. In addition to this digitized wireline
transmit audio being sent to the APX transceiver to be transmitted, it is also sent on the CAN_AUDIO
bus to the O5 control head (for APX Consolettes with the local control option). The O5 control head
converts this digitized audio to an analog signal and processes it through a Class D audio PA circuit
before sending it to the Consolette's local 20 Ohm speaker. Refer to
speaker operation.

2.3.16.4 Transmit Audio Routing to Remote

In addition to the digitized rear panel transmit audio and local microphone audio being sent to the
APX transceiver to be transmitted, some of these paths can also have this same transmit audio
routed back through the Codec and output as analog audio out the wireline, out the Recorder
interface, and/or out the External PA interface. Analog transmit audio from the headsets'
microphones, APCO AUX_TX (but not crosspatch transmit audio), and the local microphone can be
sent back through the Codec and output as analog audio down the wireline to a remote device. This
feature is enabled in the "Local Microphone Audio Routing to Remote Console" in the Consolette
Configuration Audio Parameters page. All transmit audio sources (Consolette rear panel and O5
control head local microphone) can be routed to the Recorder and/or External PA interfaces. If
transmit audio is needed on the Recorder interface, "Record RX+TX" can be enabled for "Recorder
Configuration" from the Consolette Configuration Audio Parameters page. Alert tones such as talk-
permit tones are always present in the recorder audio. Similarly, if transmit audio is desired on the
External PA interface, "Output RX+TX" or "Output RX+TX (with tones)" can be enabled for "Public
Address Amplifier Audio" in the Consolette Configuration Audio Parameters page. As indicated, alert
tones can be filtered from the External PA interface if necessary.

2.3.16.5 Transmit Indication

Finally, there is an active low transmit activity output which indicates when the APX transceiver is
active and transmitting. TX_ACTIVITY* (driven low by open drain MOSFET Q1810 when the APX
transceiver is active and transmitting) is located on the low speed connector board's DB25
Accessories Connector J104 pin 1.
September 9, 2011
Theory of Operation: System Communications Overview
section 4.4 for local front panel
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