Motorola APX 7500, Подробное руководство по обслуживанию

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68009482001 September 9, 2011
Theory of Operation: System Communications Overview 2-11
2.3.15.5 External Speaker Receive Audio
There is a secondary speaker (referred to as the external speaker) output on the low speed
connector board’s 14-pin Terminal Connector J103 pins 1 (E) and 2 (EXT_SPKR-). The
audio source for these pins originates from the J600 connector on the APX mobile’s TIB. J600 pin 24
is the APX mobile SPEAKER_LOW and J600 pin 25 is the APX mobile SPEAKER_HIGH. This audio
is passed from the APX mobile TIB through a ribbon cable onto the APX Consolette main board
through P600 connector pins 22 (EXT_SPKR-) and 24 (E). From here, the audio is
passed unaltered directly through the main board to the low speed connector board. The external
speaker audio is used to monitor receive audio and alert tones; however, this output cannot provide
transmit audio. Its audio level may be set in the APX mobile CPS to either maintain a fixed volume,
or to track the O5 volume knob. Additionally, there is an external speaker active output which
indicates when the external speaker is unmuted. EXT_SPKR_ACTIVITY* (driven low by open drain
MOSFET Q1804 when valid audio activity is present on the secondary speaker) is located on the low
speed connector board’s DB25 Accessories Connector J104 pin 23.
NOTE: EXT_SPKR- and E should never be grounded. If they are grounded, this will
damage the radio.
2.3.15.6 Front Panel Speaker Receive Audio
APX Consolettes with the local control option have an O5 control head and 20 Ohm speaker
(referred to as the internal speaker) located in the front panel. Receive audio is routed over CAN
from the APX transceiver to the O5 control head where it is converted to an analog signal and
processed through a Class D audio PA circuit before being sent to the Consolette’s local 20 Ohm
speaker. The receive audio at this speaker is volume controlled via the O5 volume knob. Refer to
section 4.4 for local front panel speaker operation. Additionally, there is an internal speaker active
output which indicates when the internal speaker is unmuted. INT_SPKR_ACTIVITY* (driven low by
open drain MOSFET Q1805 when valid audio activity is present on the local speaker) is located on
the low speed connector board’s DB25 Accessories Connector J104 pin 22.
2.3.16 Transmit Audio Path
The Consolette supplies several transmit audio paths on the rear panel of the Consolette as well as
an O5 control head paddle microphone for APX Consolettes with the local control option. The three
main input paths for rear panel transmit audio are headset microphone, crosspatch/APCO, and
wireline; however, only one of these inputs can be active at a time. All three paths originate as
analog audio at either the low speed or high speed board rear panel connectors and are sent to the
Codec (U505). Associated with each path’s audio, there are PTT sources also located on the low
speed (PPLN7787) or high speed (PPLN7786) board rear panel connectors. Headset microphone
audio is input at Codec MICIN (U505 pin 18), crosspatch/APCO audio is input at Codec INP1 (U505
pin 23), and wireline audio is input at Codec INP2 (U505 pin 19). From these inputs, the analog
audio is converted to digitized SSI audio and routed to the DSP. The primary constraint on rear panel
transmit audio is that only one Codec input can be visible to the DSP at any given time. Based on the
Consolette Configuration "Rear Panel Priority" audio parameter, a priority is assigned to the inputs to
determine which one is routed. If "None" is selected then audio is routed on a first-come first-served
basis. All three paths have separate transmit gain controls within the Codec and DSP which can be
adjusted using the Consolette Configuration. These gains can be adjusted from -42 dB to +20 dB in
0.5 dB steps to achieve the desired transmit deviation. If “TRC” is selected as the “Wireline Function”
audio parameter in the Consolette Configuration, the DSP will filter the TRC guard tone from the
transmit audio.