Motorola pro7100 Manuel de service télécharger pdf (Page 29)

Theory of Operation 2-15

2.3.5.4 Handset Audio

Certain accessories have a self contained speaker which requires a different voltage level than that

provided by U0271. For those devices, HANDSET AUDIO is available at control head connector

J0401, pin 7.

The received audio from the output of the ASFIC CMP’s digital volume attenuator and buffered by

U0211, pin 1, is also routed to U0211, pin 9 where it is amplified by 20 dB. This is set by the 10k/

100k combination of R0261 and R0262. This signal is routed from the output of the op amp U0211 to

J0401-7. The control head sends this signal directly out to the microphone jack. The maximum value

of this output is 6.6Vp-p.

2.3.5.5 Filtered Audio and Flat Audio

The ASFIC CMP audio output at U0221, pin 39 is filtered and de-emphasized, but has not yet gone

through the digital volume attenuator. From ASFIC CMP U0221, pin 39 the signal is routed via

R0251 through gate U0251, pin 12 and AC coupled to U0211, pin 2. The gate controlled by ASFIC

CMP port GCB3 (U0221, pin 35) selects between the filtered audio signal from the ASFIC CMP at

pin 39 (URXOUT) or the unfiltered flat audio signal from the ASFIC CMP, U10, pin 10. Resistors

R0251 and R0253 determine the gain of op amp U0211, pin 2 for the filtered audio while R0252 and

R0253 determine the gain for the flat audio.The output of U0253, pin 7 is then routed to J0501, pin

11 via dc blocking capacitor C0542. Note that any volume adjustment of the signal on this path must

be done by the accessory.

2.3.5.6 RX Secure Audio Option

Discriminator audio, which is now encrypted audio, follows the normal receive audio processing until

it is output from the ASFIC CMP UIO (U0221, pin 10), which is fed to the secure audio board at

option connector J0551, pin 35. On the secure board, the encrypted signal is converted back to

normal audio format, then fed back through J0551, pin 34 to AUX RX of the ASFIC CMP (U0221, pin

43). The signal then follows a path identical to the conventional receive audio, where it is filtered (0.3

- 3kHz) and deemphasized. The signal URX SND from the ASFIC CMP (U0221-39) also routed to

option connector J0551, pin 28, is not used for the secure board, but for other option boards.

2.3.5.7 Option Board Receive Audio

Unfiltered audio from the ASFIC CMP (U0221, pin 10) enters the option board at connector J0551,

pin 35. Filtered audio from the ASFIC CMP URXOUT (U0221, pin 39) enters the option board at

connector J0551, pin 28. On the option board, the signal is processed, then fed back through (J0551,

pin 34) to AUX RX of the ASFIC CMP (U0221, pin 43). The signal then follows a path identical to

conventional receive audio, where it is filtered (0.3 - 3kHz) and de-emphasized.

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Motorola pro7100 Manuel de service Page 29