• Review: CPFlight Modules

    ATC Radio / Transponder

    The ATC radio module is also known as the transponder module in aviation. Transponder is short for transmitter-responder and is also sometimes abbreviated to XPDR, XPNDR, TPR or simply just the TP.

    The function of the ATC module is to send out a response signal when receiving a radio-frequency interrogation from e.g. a tower controller. These response signals are also known as "Squawk codes".

    This enables the tower controller to assign a number to a specific dot on the towers radio monitor or CAS and hereby being able to keep aircraft clear of each other when flying in controlled airspace.


    The ATC module features one combined digital display showing the squawk code, failure and XPNDR number. To control this display the module has two dual concentric rotator switches each with both an inner and an outer knob - these rotator switches controls the digits of the squawk code.

    Together with these rotator switches the ATC also features an XPNDR switch which controls the specific transponder to use as e.g. XPNDR 1 or 2. Additionally there is also an ALT Source switch which enables the pilot to select data information to the modules from two different sources which is either the Air Data Computer No1 or No2.

    On the ATC module there is also located a 5-step rotator switch which controls if the ATC is on/off and also how detailed the response signal will be. I have listed the specifics here below:

    • STBY: The transponder in in standby mode/off and does not transmit
    • ALT RPTG OFF: The transponder does not send altitude information
    • XPNDR: The transponder is active and also sends altitude information
    • TA ONLY: Activates traffic alerts / warnings
    • TA/RA: Activates traffic alerts / warnings and advises about target resolutions

    The last features found on the ATC module are the failure light which will light up in a red color if the transponder fails to send out the response signal. This will also be visible inside the digital display where the letter "F" will be added to the left of the squawk code.

    In between the two dual concentric rotator switches there is located a small push button named IDENT. By pressing this button the pilot can manually send out the response signal which otherwise is done automatically every second or so. The specific time interval I do not know.

    On the back of this module there is not much to see - only the two DIN connections and they work the same as the COM radio. One is used for input and the other for output - which you use for input or output doesn't matter; whatever fits your setup the best.

    Look and feel is similar to the COM radio. The ATC module is also build of a PCB with all the toggle switches, the rotator switches and the digital display mounted directly on it, and placed on a laser cut aluminum front plate with engraved legends. The ATC module also features a backlight function with can be controlled by the BRT modules later described in this review.

    I compared the CPflight ATC module against the animated PMDG B737NGX ATC module and found them to be identical. The ATC module is fully operational and all switches and functions are correctly applied to the animated version which then carries out the command within FSX.

    Using this module certainly also added a huge amount of realism because I now did not need to select the specific squawk codes on the animated ATC but now instead I had a real piece of hardware to use. This I would recommend if you are a serious flight simmer that really enjoys flying a flight as realistically as possible with the full integration of the ATC.

    Using the ATC module with the ATC window was just like with the COM radio - when e.g. the tower controller or another information service asked me to squawk a specific code, I just tuned this in the transponder and the information was send and received without me even having to use the numeric code in the ATC window - this was awesome but if this is due to the module or a feature within FSX I am not sure, but the realism I got was superb!

    The connection of these modules was extremely simple - just connect the DIN cable and the ATC module was working instantly. There is no need for additional drivers or programming - everything was working perfectly when the DIN cable was connected. Of course no CPflight modules that I have tested can work without the flight simmer gives the modules the correct communication port of the computer, but this only has to be done one time which will cover all modules (because they are all connected on a string and only have one USB connection)

    Another superb thing that I discovered using this ATC module was that the selections area was limited to only include the number 0-7 which is perfectly aligned with the real ATC module. This is again just a small detail but it does tell me a lot about how thorough and detailed the team at CPflight really is - they do not compromise but goes all the way and that I like very much!

    Tags: cpflight

    1. MBUNJES's Avatar
      MBUNJES -
      Nice review.
      I miss the information about the TCAS test function of the transponder, does it work or doesn't it?
      About the stab trim and flood panels: they are exactly like the real thing, the airline orders their own version so you always get different versions in different airlines.
    1. RaysAviation's Avatar
      RaysAviation -
      Quote Originally Posted by MBUNJES View Post
      Nice review.
      I miss the information about the TCAS test function of the transponder, does it work or doesn't it?
      About the stab trim and flood panels: they are exactly like the real thing, the airline orders their own version so you always get different versions in different airlines.

      Hi, yes I did a follow-up on the stab trim and found that they are actually very realistic. It seems that there just are several versions and what CPFlights did, was the newest version and what I found during the test was an older version. This however does not change my rating since the BRT modules are mostly eye candy.

      The TCAS - I am not sure what you mean, but I can say that all rotator switches, toggle switches and the push button all activates the corresponding button/switch in the virtual ATC when using PMDG737NGX. But some really nice modules for sure which bring a lot to the flightsim experience in my opinion.

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