BB-HCM715CE, BB-HCM735CE - Panasonic Video Monitoring Service Manual (repair manual). Page 15

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PCM Codec and Video Amplifier (IC501)
Power Supply Voltage: 3.3V
Clock Frequency: Contains a built-in PLL function and generates a clock from the 2MCLK supplied from IC101.
I/F with Host: Controlled by I2C.
Audio Block: Contains an amplifier, LPF, gain adjustment, AD/DA converter, PCM serial I/F and speaker output function.
Image Block: Contains an analogue video amplifier (6dB).

External Microphone Jack (JK503)
Used with the external microphone.
When the external microphone is not inserted, the MIC_S signal goes HIGH.
When it is inserted, the MIC_S signal goes LOW, the CPU (IC101) detects the microphone status and controls the microphone
SW on and off in the PCM Codec (IC501).

Audio Output Jack (JK504)
Used when connecting a speaker with a built-in amplifier, when the audio is output from a camera.

Analogue Video Output Jack (JK502)
Used when connecting with TV or Video equipment.

Flow of audio Signal
[Microphone audio]
The audio signal input from the built-in microphone and the external microphone is amplified by the amplifier in the PCM Codec
(IC501), with AD conversion and gain adjustment performed.
The sampling frequency of the AD conversion is 8kHz and it is converted to the PCM in the format of 8bit and 

µ law. Then,

64kbps data are output to the IC101 on the CPU board through the Serial I/F.
The data transfer of the Serial I/F is BCLK (256 kHz).

[Speaker audio]
The audio data are sent from the network and after data decompression in the Audio I/F block (IC101), the data are transferred
as the audio 64kbps data to the PCM Codec (IC501) through the Serial I/F.
After the 

µ law to linear conversion, amplification and DA conversion, they are output (JK502) as audio output signal in the PCM

Codec (IC501).