Vega Telex HB-3PLUS Technical Manual - 4 Theory of Operation
HB-3plus Headset Adaptor Box
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4 Theory of Operation
4.1 Console Mode
With JMP8 in the “B” position the HB-3PLUS will operate in the console mode. All PTT and headset
audio is routed to the console jack (J1) for connection to the handset jack of any Vega consoles using the
supplied 4-pin modular cable.
Headset I TX audio is amplified for connection to either the console or NENA interface, during radio PTT
the TX audio and PTT signals are sent to the console. If the NENA interface is OFF-Hook, The HB-
3PLUS signals the console and SELECT audio is routed to the console speaker. The NENA RX audio is
routed to the headset earpiece and the headset microphone is routed to the to the NENA TX circuit, if
PTT is pressed the headset microphone is switched to the console TX circuit and console PTT is applied.
4.2 PC Mode
With JMP8 in the “A” position the HB-3PLUS will operate in the PC mode. All PTT and Monitor actions
are routed to the serial port and sent to the PC as serial commands. Headset and desk microphone
audio is routed to the MIC OUT jack.
Headset I TX audio may be switched to either the PC or NENA interface. While radio PTT is active, the
TX audio and PTT signals are sent to the PC. If the NENA interface is OFF-Hook, Selected radio RX
audio is switched to the PC speaker. With radio PTT not active, The NENA RX audio is routed to the
headset earpiece and the headset microphone is routed to the to the NENA TX circuit. When radio PTT is
pressed the headset microphone is coupled to the PC MIC OUT circuit and PTT serial command is
applied to the PC.
5 Schematics and Parts Lists