Motorola pro7100 Manuel de service télécharger pdf (Page 50)

2-36 Theory of Operation

2.10.7 Microphone Connector Signals

Signals BUS+, PTT IRDEC, HOOK, MIC, HANDSET AUDIO, FLT A+, +5V, and two A/D converter

inputs are available at the microphone connector J0811. Signal BUS+ (J0811-7) connects to the

SBEP bus for communication with the CPS or the Universal Tuner. Line MIC (J0811-5) feeds the

audio from the microphone to the radio’s controller via connector J0801-4. The Line HANDSET

AUDIO (J0811-8) feeds the receiver audio from the controller (J0801-6) to a connected handset. FLT

A+, which is at supply voltage level, and +5V are used to supply any connected accessory like a

microphone or a handset.

The two A/D converter inputs (J0811-9/10) are used for a microphone with keypad. A pressed key

changes the dc voltage on both lines. The voltages depend on which key is pressed. The µP

determines from the voltage on these lines which key is pressed and sends the information to the

host radio.

Line PTT IRDEC (J0811-6) is used to key µP the radio’s transmitter. While the PTT button on a

connected microphone is released, line PTT IRDEC is pulled to +5 volts level by R0843. Transistor

Q0843 is switched on and causes a low at µP port PA2. When the PTT button is pressed, signal PTT

IRDEC is pulled to ground level. This switches off Q0843 and the resulting high level at µP port PA2

informs the µP about the pressed PTT button. The µP informs the host radio about any status

change on the PTT IRDEC line via SBEP bus.

When line PTT IRDEC is connected to FLT A+ level, transistor Q0821 is switched on through diode

VR0821 and thereby pulls the level on line ON OFF CONTROL to FLT A+ level. This switches on the

radio and puts the radio’s µP in bootstrap mode. Bootstrap mode loads the firmware into the radio’s

flash memory.

The HOOK input (J0811-3) informs the µP when the microphone´s hang-up switch is engaged.

Depending on the CPS programming, the µP may take actions like turning the audio PA on or off.

While the hang µp switch is open, the line HOOK is pulled to +5 volts level by R0841. Transistor

Q0841 is switched on and causes a low at µp port PA1. When the HOOK switch is closed, the HOOK

signal is pulled to ground level. This switches off R0841and the resulting high level at µp port PA1

informs the µp about the closed hang µp switch. The µp informs the host radio about any status

change on the HOOK line via SBEP bus.

2.10.8 Speaker

The control head 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

J0801-10, 11 to the speaker connector P0801, pins 1 and 2. The speaker is connected to the

speaker connector P0801. The control head speaker can be disconnected only if an external

speaker, connected on the accessory connector, is used.

2.10.9 Electrostatic Transient Protection

Electrostatic transient protection is provided for the sensitive components in the control head by

diodes VR0811 VR00812 VR0816 - VR0817. The diodes limit any transient voltages. The associated

capacitors provide radio frequency interference (RFI) protection.

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Motorola pro7100 Manuel de service Page 50