Are direct connect head phone jacks required?

I have a two place panel mount intercom. The installation instructions show the intercom connecting to an existing jack set, which has been confusing to me. I called tech support and we chased out tails for awhile. His perspective was adding the intercom to an installed radio, my newbie perspective is from installing a new and complete system.

He said there was no technical reason I could not wire the radio directly to the intercom BUT he thought the FAA required the radio had to have its own set of jacks. Does the FAA require a set of jacks wired directly to the radio? I am not going to have an external sepeaker if that makes any difference. Thanks.

There is no requirement for jacks to be wired directly to the radio. Most all intercoms have a fail mode that connects the jacks directly to the radio.
Mel...DAR

Mel's right about the fail-safe deal, however I still put in a separate jack that goes straight to the radio. This way if the intercom should ever have to be removed for service or replacement, I can still fly the plane.

Steve Zicree
RV4

What Brand

Just for grins what Brand make model are you dealing with. Sounds like tech support might lead you a little a skew? The two intercoms I wired in the past (DRE and PS Engineering) showed only the jacks out of the intercom.

True, you don't need a separate headphone and/or Speaker / mic jack in an experimental. Old school thinking was to have these items. In experimental's we wire direct to the intercom (or thru it I might say) to the intercom head phone jack / mic (PTT combined) jack.

Old school is fine but what is the likely hood the headset, PTT will fail. Well if using high quality components very unlikely. Carry a second headset (which you may already have for passengers) and have two PTT's wired (also pretty common , one for pilot, one for co-pilot).

The planes I fly at work have both head set/ PTT on yoke and speaker and separate mic. It is nice to take the headset off in cruise and go to speaker and use the hand mic, but the cockpit compared to a RV is much more quite. Forget the speaker and separate mic, you don't need it. G

Intercom

McFly:

You didn't say what type of intercom you are using. Some intercoms do not 'fail safe'. In this situation, the direct connect jacks could be useful.

Other types (like Sigtronics), can be made 'fail safe', working during power off mode, or even when removed from the panel. This requires a two-pole switch to connect pilot mic to radio mic and pilot transmit key to radio transmit key. The headphone audio does not need to be switched, and all other audio sources (radios, alarms etc.) will work properly.

Alternatively, a second set of jacks and transmit key switch can be provided.

What I did in my airplane was provide panel mount jacks and a transmit key. My main headset plugs are in the armrests. In the event of an intercom failure, I can swap the headset connection and use the panel transmit key switch.

I always ask 'what happens when it fails, and what's my backup'. Backups don't have to be elegant, they just have to work.

For more details, the vx Aviation AMX-1A Audio Bus device has some schematics at the end of the .pdf datasheet. FMI: http://vx-aviation.com/page_2.html#AMX-1A_more


Vern Little
RV-9A

You get what you pay for

vlittle said:

McFly:You didn't say what type of intercom you are using. Some intercoms do not 'fail safe'. In this situation, the direct connect jacks could be useful. Vern Little RV-9A

Click to expand...

Good point Vern, but IMO if your intercom does not have a fail safe pass through feature, don't buy it or sell it; buy one that does. Don't cheap out on the intercom. DRE, PS Engineering are excellent choices. There are other good brands, I am just familiar with these two. I know there are cheaper intercoms and if they don't have this basic safety features they are lacking in other features and sound quality. I found cheap intercoms sound cheap and are annoying. The intercom is the KEY to your communication to ATC and passengers and you use it every flight all the time. Well worth the investment. G

Avcomm

Thanks for the clarification everyone

I am using an AVCOMM AC-6PA intercom, which does have the ?fail safe? feature when intercom power is off.

One of the reasons why I went with AVCOMM is that most of the harness work is already done for you (at the time of purchase I could not imagine doing this wiring myself but I would tackle it myself if I could do it again). The pilot and co-pilot phone harness are ready made units. The documentation references phones that are not the AVCOMMs. Usually I feel dumb when I make a call to the tech guys because feel I should be able to figure it out myself; in this case the doc was misleading IMHO.

I am going with two head sets with a single PTT on the pilot side stick. Thank you all for your help.

Install manuals

McFly said:

I am going with two head sets with a single PTT on the pilot side stick. Thank you all for your help.

Click to expand...

Cool One PTT on pilot side. That is all you need, but may I suggest that you put another PTT on the panel (if side-by-side).

The reason is it is cheap, light and if you fly with another pilot or get a bi-annual the CFI may need a PTT**. If the PTT fails (unlikely but happens) you have the other button.

George

**However I just remembered you could us a portable PTT (one of those buttons with the Velcro) in-line with the mic jack on the copilot side for temporary use for another pilot/instructor when needed.

Hmmmm..interesting thread....

Do as others have said and stick with a good intercom. We wire up a lot of audio panels and intercoms and have come to really like some and really dislike others for a variety of reasons.

My favorite (and my techs) is the PS engineering stuff. Top notch, easy to wire up and good functionality. The NAT's, DRE's and surprisingly Flightcomms are next on our list.

There are only a few intercoms I dislike or we don't want to wire up anymore for various reasons. For example, Sigtronics uses a couple wonky connectors that are stuck on some bizarre 6" pigtails with weird pins (read Not standard Dsubs). Second, the wire they include for their "harness" is cheapo PVC wire...not aircraft grade and not shielded. Also not a big fan of the Softcoms and Avcoms or a few others.

Spend a few extra bucks on a good intercom and you'll be happy you did. The name brands like PS Engineering have excellend functionality, top notch customer service & support (what other company president to you see hanging around "builders forums" to answer questions in his personal time?), and their documentation is great.

I may sound a bit biased, but I can say that my bias has grown from experience of wiring a lot of intercoms ranging from old antique crap to the nice new PSE/ect.. stuff.

Just my 2 cents as usual,
Stein.

For what it's worth, I recently wired a PS Engineering intercom and it said in the install manual that aux jacks are required. I'm not sure by what authority they say that, but it is there. Also, if you have a pilot PTT failure and use the passenger PTT, it will switch the radio to transmit but WON'T connect your mic. In this situation you'd have to have the presence of mind to swap headsets (or at least swap jacks). This is definitely the kind of thing that's good to know before the situation arises.

Steve Zicree
RV4 finishing

Intercoms are a pain to wire. Most of them do not have enough inputs or grounds to eliminate the 'forest of tabs' that others have complained about.

Using the AMX-1A with the Sigtronics intercoms solves all of the problems you mention (converting the Sigtronics box connector to D-subs with dozens of extra ground leads and providing up to 10 audio inputs and providing a seperate connector for off-panel headsets).

This combination is less expensive than most intercoms and quite a bit easier to install, especially if you want to make a removable panel.

It still surprises me that intercoms are so expensive, given what they are. Some radios (SL-30/SL-40 for example) have built in intercoms, but apparently they don't work so well in noisy environments. It would make a lot of sense for these to be improved... thus eliminating another instrument on the panel, and it's cost. That will allow even more room for big-screen TV's/EFIS systems.

FMI http://vx-aviation.com/page_2.html#AMX-1A_more

Vern Little

Built in Comm Radio intercoms

Most Comm radios have a "Built in intercom". My feeling from the one or two I have seen, they are ALL FEATURE fillers for their marketing brochure, to be competitive with all the other radios with so called Intercom's. To talk you have to press the PTT. The ones I have seen are NOT VOX or voice activated. The intercom does not work with the radio. You have to throw a switch between intercom PTT (mic) or radio PTT mic (switch selects what the PTT will do, transmit or intercom). In other words it's a VERY basic-bare bones deal (not practical for us). In a word, it's an intercom in name only.

The intercom, a good one at least has separate channels or amplifiers for each channel so only the mic that is spoken into opens. Many cheap-O's have one amp and every mic opens when one does, which is more noise. The good ones allow all kinds radio/aux input (music)/crew-pilot-pax isolation/override features and combinations, plus have separate volume and squelch controls for each mic. Also like good stereos, good intercoms have amplifier's of higher power and fidelity, found on the higher price units. That is just part of the picture. George