Frequently Asked Questions

1U619-() / 1U661-() Radio Control Panels

We are currently making studies on Mode S transponder retrofits for some Cessna Citations including C500, 502, and 550. Since some of these airplanes have your digital radio panel installed,  we need to come with a solution for Mode S transponder (mostly Collins TDR-94D –007) with elementary surveillance (Flight ID) functionality for the European airspace. Do you offer a replacement controller for the existing transponder controller installed in your radio panel? Currently installed: P/N 1U619-001, -002, and –003. If you have a solution for Mode S elementary surveillance, please let me know some details. Lead time and pricing. Otherwise we would have to replace the complete radio panel and install individual Collins controls. This would be very costly and the customers would not be very happy to remove a two year old radio panel. There is not much time for the Mode S. Due to an extension of the mandate, we have good luck. Definitely by March 2004 (sic), all these airplanes have to be compliant.

Best regards,
M.W., ACS Aviation Consulting Services,


Thank you for your e-mail, and we can understand why your customer would be upset if he had to replace his 1U619-001 after only two years of service. Working in conjunction with Cessna (Wichita, KS), we have decided for many good reasons that to accommodate a new Mode S transponder (and perhaps TCAS) it would be best to modify the 1U619-001 RCP by replacing the ATC transponder function with that of an ADF. This would allow either of the Collins or Honeywell control heads to be installed in the location vacated by the ADF. There are several benefits with this approach. First, there would be fewer potential problems during system integration. We have always assured compatibility between our control heads and any other manufacturer’s radios, but by using the manufacturer’s own components, future changes, mods, etc. would be easier and less expensive to implement. Secondly, the old, mechanical Edo Aire ADF control head has long been obsolete. We no longer manufacture it nor do we support it in any way. By removing the antiquated control and replacing it with a fully supported and warranted digital equivalent, serviceability and full support is assured. Additional functionality (such as memories, pre-select, etc.) is also realized. The two Edo Aire part numbers affected are: 156M1 (single), or 152-10 (pre-select). Lastly, it is not practical to replace our 1U619-001 with individual Collins control heads because of the legacy equipment still onboard. The two NAV/DME legacy receivers require ARINC 410 ‘2 out of 5’ tuning. Collins no longer manufactures its original Proline head (which was ‘2 out of 5’), so you would have to find some on the surplus market. Note that Proline II heads output CSDB serial data only. Obvious difficulties arise with this approach including service, warranties, etc, and that’s if you can find an acceptable, used controller. In fact, it was mainly for this reason that the 1U619-001 was developed, not just for the two NAV/DME radios but also for the two legacy transponders (TDR-90) which are tuned with octal, parallel busses.

If you are interested in this approach, please notify us. At this time, we are not planning on adding Mode S / TCAS capabilities to the existing 1U619-001. The new RCP part number is 1U661-001. It is identical to the 1U619-001 except that the ATC module has been replaced with an ADF. Thank you.

FJS – 2/16/2004


We are modifying a Citation II equipped with your box, adding in particular TCAS:CAS67.
Could you please let me know if you already supply the mod for mode S/TCAS or have the possibility to replace the XPDR part with ADF control head, and which conditions.

Y. L., VP-GM, Uni Air Entreprise
Paris Le Bourget

A: You asked two distinct questions which I have answered here:
  1. A mod to accommodate Mode-S/TCAS in the 1U619-001? At present, there are no plans to supply such a Mod.
  2. A mod to replace existing ATC with an ADF head? Yes. The 1U661-001 would replace the 1U619-001. The ATC head in the 1U619 is replaced by an ADF head, (functionally equivalent to a 156M1.) The resulting unit is a 1U661-001.
The cost is about a 1/3 of a new radio control panel, and we can work out an exchange to minimize your down time.  If you are interested, please notify us and we will be happy to give you all the details.

FJS – 5/19/2003

We are working on a Cessna Citation 500 that is equipped with the 1U619-002 control panel. We now have to change the built-in Transponder with a new Mode-S transponder. Because this new Mode-S transponder is bigger than the old one and therefore does not fit into the control panel, we want to replace the old transponder with the ADF. We will then mount the Mode-S transponder into the place where the ADF was.  Do you have a kit and a service bulletin for replacing the built-in transponder of the 1U619-002 control panel by the ADF?

 C.M. Mueller, Kuerzi Avionics AG, Flugplatz

Thank your for your e-mail. In it you reference a part number 1U619-002. This control panel does not have VHF COMM controls with 8.33 KHz frequency spacing. Perhaps you meant the 1U619-001 which does, and is the panel that we sell mostly to the Europeans. In either case, we are introducing the 1U661-001 and 1U661-002 to replace the 1U619-001 and 1U619-002, respectively. The only difference between the panel types is that the ATC transponder control in the 1U619 –( ) is replaced with an ADF control as you suggested. We are not offering a mod, but you can send in your old 1U619-( ) and we will convert it into a 1U661-  ( ) with a new warranty. The cost is about a third of new radio control panel. Contact us again if you have any interest. We can work out an exchange to minimize your down time. Thanks again.

FJS – 3/10/04

We have the following documentation for the Electronic Control Panel 1U619-001 CMM with IPC. P/N: 86M068, Issue 0, 3/28/03. Is this the current version of the manual, and are there any Service Bulletins for the Manual available?

M.S., Avionics Inspector, RUAG Aerospace Services GmbH

You have the current version of the manual, and there have not been any Service Bulletins issued at this time. Refer to the Documentation for the latest revisions.

FJS – 2/10/2004

Since we have to evaluate feasibility  to quote some installation of Mode-S transponder in Cessna Citation 500 we still require your kind concurrence  in sending us the following info: simple information about the changes applied to the new panel such us panel pin out, panel layout, picture of the panel, two sentences on the differences from the old and the new panel.
Thanks a lot for your prompt help.

G. L.,  Northern Avionics, Italy

The original mechanical radio control panels were manufactured by Edo Air. The part number for the Edo control panel was a 1U434-001. The Sigma Tek electronic replacement is a 1U619-002, and is pin compatible with the mechanical units except for the requirement of power for the ATC transponder control head. (The mechanical heads didn’t require aircraft power, but it was available in all heads via the power on/off switch except for the ATC. This requires the addition of two wires.)

The European mandate to employ VHF COMM communications transceivers with 8.33 KHz channel spacing back in 1999 resulted in the development of the 1U619-001. Sigma Tek worked with Cessna on this project. Cessna purchased a significant number of these controls, and obtained exclusive rights to the product. They offer a basic upgrade kit which consists of two Collins VHF COMM transceivers, the 1U619-001, and a wiring harness. They have a Service Bulletin which covers the entire upgrade.

Next March 2005, another European mandate is going into effect which requires transponders with Mode-S functionality. This requires that the radios be replaced, and a suitable control head be installed. After careful consideration, Sigma Tek and Cessna made a joint decision to implement the Mode-S upgrade in the following fashion: the transponders are replaced, the 1U619-001 is converted into a 1U661-001 in our facility for a minimal charge, the old mechanical Edo 156M1 ADF control panel (which is obsolete and no longer supported) is removed creating a space for the new transponder control head, and the harness is installed for the new transponders. The existing ADF control head wiring and connector are routed to the ADF control in the new 1U661-001. The electronic and mechanical ADF heads are 100% pin compatible. This makes for a neat, efficient, and trouble-free installation. 

FJS – 5/18/2004

Do you know if Cessna is going to issue a Service Bulletin that addresses the Mode-S/TCAS upgrade for the Cessna 550?

T.G., Advanced Avionics Systems

Yes, the Cessna Service Bulletin numbers are listed below.