Motorola CM340 Сервісна інформація - Сторінка 12

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Також для Motorola CM340: Посібник користувача (24 сторінок), Посібник користувача (5 сторінок), Посібник користувача (12 сторінок)

2-6

The HOOK line (J102-6) is used to inform the uP which type of microphone or SCI lead is connected

to the microphone socket. The voltage of the HOOK line is monitored by the uP (port PE0,

MIC_SENSE) through a resistor divider on the main board. When the HOOK line is grounded (on

hook condition) or floating (2.8V nominal), the uP sets the mux (U8) for keypad operation to allow the

use of microphones with a keypad. When the HOOK line is connected to 9.3V, the uP sets the mux

for SCI operation. This mode is also used to select low cost mic operation where the gain of the

microphone path is increased (on the main board) to compensate for not having a pre-amp in the low

cost mic.

If the BOOT_RES (J102-7) line is connected to >5V (e.g. 9.3V) at turn-on then the uP will start in

boot mode instead of normal operation. This mode is used to programme new firmware into the

FLASH memory (U404 mainboard).

3.7

Speaker

The controlhead contains a speaker for the receiver audio. The receiver audio signal from the

differential audio output of the audio amplifier located on the radio's controller is fed via connector

J103-1, 2 to the speaker connector P101 pin 1 and pin 2. The speaker is connected to the speaker

connector P101. The controlhead speaker can be disconnected if an external speaker, connected on

the accessory connector, is used.

3.8

Electrostatic transient protection is provided for the sensitive components in the controlhead by

diodes VR1 - VR4. The diodes limit any transient voltages to tolerable levels. The associated

capacitors provide Radio Frequency Interference (RFI) protection.

THEORY OF OPERATION