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SPA-600N INSTALLATION AND OPERATING INSTRUCTIONS (For Very High Noise Applications) - page 1 / 2





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The Sigtronics’ SPA-600N is a voice actuated intercom with “transmit through the aircraft radio capability” using your push-to-talk switch. Three controls are provided:

Power Switch — Turns unit on and off. Volume Control — Controls the intercom volume. Squelch Control — Allows the setting of voice actuated (VOX) operation of the intercom for variations in background noise levels and differences in headset microphones.


  • I.


    • A.

      Put on headset/s and position the boom mic close to the mouth, as is the practice with a hand-held mic. Voice clarity is best when mic is at one side of the mouth and 1/4” from the lips.

    • B.

      Set audio panel to “Headphone” position, if applicable.

    • C.

      Turn power “on” and set Volume Control to a low level. (1/4th to 1/3rd open for best signal to noise ratio).

    • D.

      For voice activated intercom adjust Squelch Control clockwise until back ground noise becomes audible. Then rotate counter- clockwise small amounts until the noise diminishes. Now make small, incremental adjustments until voice triggers unit on. This procedure is necessary because the squelch system is a “fast on, slow off” circuit.) Small adjustments may be necessary if aircraft background noise changes significantly. To use the push-to-intercom feature, turn the squelch control on the intercom fully counter-clockwise. Then to activate, push the ICS push-to-intercom switch.

  • II.

    RADIO TRANSMIT MODE — Transmitting from both pilot and co-pilot positions is possible on a one-at-a-time basis. The transmitting mic disables all other mics. When you are ready to talk to ATC, depress the transmit switch on your yoke and your voice is automatically transmitted via the aircraft radio.

You will hear your own voice when transmitting via the aircraft radio side-tone return, If the radio does not have side-tone, then you will not

Figure 1

hear your voice. A minor modification to the intercom will enable it to simulate side-tone.

  • III.

    RADIO MONITORING — Radio monitoring is automatic. The radio monitor circuit is always active; even with intercom power switch “off”.

  • IV.

    SOLO FLIGHTS — Since the intercom is not needed during solo flights, it may be turned off. The pilot will still hear the aircraft radio, since this circuit is always active, and the pilot may transmit to ATC via his push-to-talk switch. (Co-pilot position cannot transmit when intercom is off).

V. BACK-UP — If a problem is suspected in the intercom, simply turn it off. You will still receive the aircraft radio and will be able to transmit from the pilot’s position. The hand mic may also be used, however, the Transcom should be turned off and you should unplug your boom mic from the mic jack. (Leave headphone plugged in for radio reception).

CHASSIS INSTALLATION The Sigtronics’ SPA-600N has been designed to mount either horizontally or vertically in your aircraft panel. All necessary mounting hardware has been supplied for a 6-way installation. (A round faceplate is also available from Sigtronics to fit a 2 1/4” round instrument hole).


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HARDWARE SUPPLIED Six Headphone Output Jacks — Accept standard .250” aircraft headphone plugs. Six Microphone Input Jacks — Accept standard .206” aircraft microphone plugs (i.e. amplified dynamic or electret). (U93 plug compatible jacks can be used in place of the jacks provided). Mic Jack Insulating Washers: 6 flat and 6 shoulder. Panel: Lettered on both sides. Control Knobs (2), Switch Nut (1), 4-40 Screws (2) Template: Hole size pattern for drilling aircraft panel. Aircraft / Intercom interface cable (4 feet long)

The location selected requires a minimum front panel area of 2-1/2” by 1-1/16”. Depth required behind panel is 4-3/16” plus cable access. Caution: Move aircraft flight controls through limits of travel while observing selected area to make sure rear of intercom and cable will not interfere with aircraft control components.


  • 1.

    Position adhesive template on aircraft panel in selected area.

  • 2.

    Center punch each hole at cross lines. (The five holes are in straight

line and equally spaced 0.4” apart.)

  • 3.

    Drill 1/8” pilot hole all five places.

  • 4.

    Enlarge holes to 1/4” and 3/8” per template.


Sigtronics Corporation 178 East Arrow Highway San Dimas, CA 91773 Phone: (909) 305-9399 E-mail: info@sigtronics.com Web Site: www.sigtronics.com

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Figure 2


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Microphone Jack


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    Figure 3

  • 1.

    Remove nut from Transcom ON-OFF switch bushing.

  • 2.

    Remove knobs from Volume and Squelch controls. NOTE: DO NOT REMOVE nuts from Volume and Squelch control potentiometers.

  • 3.

    Remove two 4-40 panel screws and remove panel from Transcom chassis.

  • 4.

    Insert Transcom from rear of aircraft panel with appropriate arrow pointing upwards.


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