Overview
Introduction/Theory of Operation B.1-1
1.0 Overview
Hand Held Control Head PMMN4005
2.0 Theory of Operation
2.1 General
The Hand Held Control Head contains the microphone, 3 top buttons and 1 side button (PTT button)
and 22 keypad buttons to operate the radio, several indicator Light Emitting Diodes (LED) and 7
icons of LCD Display to inform the user about the radio status and 10 character (5x7dot matrix)
Liquid Crystal Display (LCD) for radio information e.g. channel number, unit or group address.
2.2 Power Supplies
The power supply to the HHCH is taken from the host radio’s FLT A+ voltage via connector J0901
pin 8. This voltage is at battery level and is used for the voltage regulator (U0971), the indicator
LEDs, the back light and to power up the radio via the On/Off button. The voltage regulator (U0971)
provides the stabilized 5 volt source for the LCD driver, the shift register, inverter and the keypad
buttons. The regulated output of U0971 is enabled by a low state and disabled by a high state at pin
3 (SHUTDOWN) to switch the HHCH circuits on and off. Input and output capacitors (C0972, C0975
and C0976) are used to reduce high frequency noise and provide proper operation during battery
transients.
.
EMERGENCY
CLEAR
ON/OFF
TOP KEYS
INDICATOR LED
PTT
FRONT MIC PORT
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