Northern Airborne Technology 270 - Manual (Page 17)

SM270 Rev. 4.10 Model 270 Universal Interface Amplifier Manual
2.3.3 Adjustments and Selections
Refer to drawing 270 Switches-Pots at the end of this section for all adjustment locations.
2.3.3.1
Trim Adjustments
Access to trim pots is through holes in the sides of the cover (see below).
THLD
MIC
SDTN
VOX MIC
GAIN
RCVR
LEVEL
MIC SDTN (VR4) Adjusts the level of MIC sidetone audio mixed from the MIC Audio input channel to the
Audio Output channel. Adjust VR4 fully CCW (10 turns) if no MIC sidetone is desired.
VOX THLD (VR3) Adjusts the activation VOX threshold for the Voice Activated Switch between the
Spare Audio input channel and the Spare Audio output channel. Set this adjustment
to full CW position (10 turns) if the External VOX threshold option is to be connected
and jumper J2 is removed.
RCVR LEVEL (VR2) Adjusts the audio level between the Audio input channel and the Audio Output channel.
MIC GAIN (VR1)
Adjusts the audio level (gain) between the Mic Audio input channel to the Mic Audio
output channel. Adjusting the MIC gain will also affect the MIC SDTN level.
2.3.3.2
Mini-Switch Adjustments
Access to mini-switches is through holes in the sides of the cover (see below).
AUDIO OUT
(8Ω) LOAD (600Ω)
RELAY
(V/L) FUNCT (K)
SPARE
(L) CTRL (V)
RELAY
(B) BIAS (G)
AUDIO OUT LOAD -
8
Ω / 600Ω (MS5)
Allows selection of 8 Ω or 600 Ω load compatibility for the Audio Output channel.
RELAY CTRL - L/V
(MS1) Allows selection of the switching relay control source between Latch (alternate action)
control and VOX (voice activated) control.
RELAY FUNCTION -
V/L / K (MS6) Allows selection of the switching relay control source between VOX/LATCH control
(VOX or alternate action) and Keyed (PTT switch).
SPARE BIAS - B/G
(MS2) Allows selection of DC MIC bias (B) or 600 Ω ground termination resistance (G) to the
Spare Input channel. Removing MS2 raises the Spare Input channel input impedance
to >10K
Ω. (see cautions in section 2.3.3.3.)
Dec 12, 2006 Page 2-3
ENG-FORM: 805-0108.DOT
CONFIDENTIAL AND PROPRIETARY TO NORTHERN AIRBORNE TECHNOLOGY LTD.