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Controlhead Model for GM140, GM340 and GM640

An additional pair of analogue lines and A/D µP ports (PE 3 – 2) is available to support a keypad

microphone, connected to the microphone connector J0811. Any microphone key press is processed

the same way as a key press on the controlhead.

2.6

Status LED and Back Light Circuit

All indicator LED's (red, yellow, green) are driven by current sources. To change the LED status the

host radio sends a data message via SBEP bus to the controlhead µP . The controlhead µP

determines the LED status from the received message and switches the LED's on or off via port PB

7 – 0 and port PA4. The LED status is stored in the µP 's memory. The LED current is determined by

the resistor at the emitter of the respective current source transistor.

The back light for the keypad is controlled by the host radio the same way as the indicator LED's

using µP port PA 5. The µP can switch the back light on and off under software control. The keypad

back light current is drawn from the FLT A+ source and controlled by 2 current sources. The LED

current is determined by the resistor at the emitter of the respective current source transistor.

2.7

Microphone Connector Signals

Signals BUS+, PTT IRDEC, HOOK, MIC, HANDSET AUDIO, FLT A+, +5V and 2 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. 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 2 A/D converter inputs (J0811-9/10) are used for a microphone with keypad. A pressed key will

change 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 up 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 will inform 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 is used to load the ﬁrmware into

the radio's ﬂash memory (See controller subsection for more details).

The HOOK input (J0811-3) is used to inform the µP when the microphone´s hang-up switch is

engaged. Dependent on the CPS programming the µP may take actions like turning the audio PA on

or off. While the hang up switch is open, 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, signal

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

informs the µP about the closed hang up switch. The µP will inform the host radio about any status

change on the HOOK line via SBEP bus.

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