Recorder And External Pa Receive Audio - Motorola APX 7500 Detailed Service Manual

Theory of Operation: System Communications Overview
Ratio) of front panel speaker maximum, 66%(1.5:1 Ratio) of front panel speaker maximum, or 50%
(2:1 Ratio) of front panel speaker maximum. Also, the minimum and maximum volume levels of the
headsets can be set using the Consolette Configuration. The "Headset Speaker Min (RX) Gain
Setting" sets the minimum volume at the headset, even when the O5 volume knob is turned all the
way down. This can be used to ensure audio is always heard at the headsets. The "Headset
Speaker Max (RX) Gain Setting" sets the maximum volume at the headset, even when the O5
volume knob is turned all the way up. This can be used to ensure the headset volume is never too
loud. The RX Audio Attenuator output is then split and sent through dual buffer op amp package
U501 (U501 pin 1 for HDST1_AUDIO and U501 pin 7 for HDST2_AUDIO) before reaching the high
speed connector board (PPLN7786) at HDST1_SPKR+ (J11 pin 7) and HDST2_SPKR+ (J12 pin 7).
Since these are both single-ended audio paths, HDST1_SPKR- (J11 pin 3) and HDST2_SPKR- (J12
pin 3) are both tied to ground. Audio levels at HDST1_SPKR+ and HDST2_SPKR+ can range
anywhere from 0 to approximately 800 mVrms based on the O5 volume knob's position. When the
headsets are disconnected, the Consolette will remove the mute override from the front panel
speaker.
NOTE: Only APX Consolettes with the local control option consisting of an O5 control head and front
panel speaker will support headsets. The limited front panel APX Consolettes will not provide
headset speaker audio.

2.3.15.2 Recorder and External PA Receive Audio

Analog audio originating from Codec OUTP2 (CODEC_OUTP2) is the receive audio source for both
single-ended recorder audio and single-ended external PA audio. Coming out of Codec OUTP2, this
audio is split and passed through recorder audio muting gate U1813, which is controlled by OMAP
output REC_ACT (U400 pin V19), and external PA muting gate U1815, which is controlled by OMAP
output EXT_PA_ACT (U400 pin N21). These muting gates unmute when there is valid audio present;
however, these muting gates can also be completely disabled via codeplug programming in the
Consolette Configuration Audio Parameters page. By selecting "Record Off" for "Recorder
Configuration" and "Output Off" for "Public Address Amplifier Audio", the Consolette will mute the
gates and not assert the associated activity outputs. The activity outputs are open drain MOSFET
logic outputs controlled by the same OMAP outputs which control the muting gates. These activity
outputs are active low logic which indicate when there is valid audio activity on the recorder and/or
the external PA paths. REC_ACTIVITY* (driven low by MOSFET Q1806 when valid audio activity is
present on the recorder path) is located on the high speed connector board's RJ45 Recorder
Connector J23 pin 3. EXT_PA_ACTIVITY* (driven low by MOSFET Q1807 when valid audio activity
is present on the external PA path) is located on the low speed connector board's (PPLN7787) DB25
Accessories Connector J104 pin 9. After passing through the recorder muting gate, recorder audio is
then sent through quad buffer op amp package U1802 (output at U1802 pin 7) before reaching the
high speed connector board at REC_AUDIO (J23 pin 1). Similarly, after passing through the external
PA muting gate, external PA audio is then sent through quad buffer op amp package U1802 (output
at U1802 pin 1) before reaching the low speed connector board at EXT_PA_AUD (J104 pin 8). Both
audio paths are at a fixed level of approximately 300 mVrms relative to a 1.0 kHz tone at 60% FSD.
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September 9, 2011