User Guide

Technical Documentation
HF Junction Box HFJ–3
Page – 3
Original 50/96
HF Junction Box HFJ–3
Introduction
The HFJ–3 hands–free junction box provides and controls the supply volt-
ages for the accessories and charge current for the handportable. In addi-
tion, it controls the audio paths to accessories and hands–free equipment.
The unit contains a protection circuit against battery voltage transients,
power switch, hands–free speaker and microphone amplifiers, audio
switches, external I/O, switch mode charger and a microprocessor which
communicates with the handportable via the mbus interface.
Main Features
Accessories Supply Voltage
Filtered and switched voltages are supplied to peripheral devices and to
hands–free audio parts in the HFJ–3 box. Protection against distur-
bances, as overvoltages, transients in incoming battery voltage.
Audio Switches
Controls audio paths between handportable, hands–free equipment and
accessories.
Handsfree Audio Amplifiers
External microphone and speaker amplifiers for hands–free operation.
Charger
Provides supply voltage and charge current for handportable.
External I/O
Open collector output, capable of driving an external relay.