gables speaker units

[dc8flightdeck]

Has anyone interface a real 737 overhead speaker unit? It appears to me it uses two wires for power, then the other four wires to mix audio inputs, possibly one set is for com audio input and the other set of wires for a warning system?

Justin

[jackpilot]

No idea
Being an avid EBay trawler, I've seen those speakers once in a while, but ended up thinking that using them was making simple things getting unnecessarily complicated.

I bought and installed real wipers though.
(Mau is right!) 

[mickc]

Hi Justin,

These speakers were used on the classics, the wiring is as follows:

Pin 1 - Speaker Audio Signal
Pin 2 - Speaker Audio Ground
Pin 3 - Muting 1
Pin 4 - 28v DC
Pin 5 - Not Connected
Pin 6 - Ground
Pin 7 - Muting 2

These speakers have an integrated amplifier which is why they require power.

The NGs use only a speaker driven by the REU, so they have only 2 wires.

[dc8flightdeck]

Thanks! Im afraid I dont understand what the muting wires are.

To be specific the unit is a G-1278. Truely a classic! 

jackpilot, my impresseion is that these are easy to use when a person understands the pinouts. In addition to the audio pots I want to be able to use the on/off switch.

Justin

[mickc]

Thanks! Im afraid I dont understand what the muting wires are.

To be specific the unit is a G-1278. Truely a classic! 

The 2 muting wires are connected together to mute the speaker.
(On the 737CL, pin 7 is grounded, which works the same way)

This is done via the ACP, so it mutes the speaker when you transmit.

Attached is the full wiring diagram from the Boeing WDM for the -300 series

[dc8flightdeck]

thank you Sir! just what I needed! 

Justin

[dc8flightdeck]

I dont know why it didnt occure for me to ask before, but do you pin information for the hand mikes? I assume when the hand mike is engaged the mute circuit in the speaker is simply closed to complete a relay circuit.

I might as well interface hand mikes while Im working on the audio system.

I just installed a 6 port intercom. Four jack stations go to four headsets inside the sim, one goes to the radome as a maintenece station (to allow communication to folks inside the sim if trouble shooting equipment), and the 6th jack port is reserved for hand mike and overhead speaker connections.

The music in/out jacks are connected to the computer for Pilot Edge coms.

[mickc]

If you are using the normal 1/4 inch plug type hand mic, then the wiring is as follows:

Sleeve - Ground
Ring - Mic Audio
Tip - PTT Switch ( Mic switch connects this to ground when depressed)

[dc8flightdeck]

Hello,
I believe youre describing a regular general aviation jack for a headset mic?

The model 603-TR hand mic on each side of the cockpit has 4 pin plugs.

[mickc]

Those Electro-voice mics came in a few different configs, usually the 4 pin was used for the PA mic.

No different really, they just have separate pins for the PTT signal instead of the shared ground used in the 3 pin config.

Pin 1 - PTT Switch 1  (pins 1 ans 2 are connected when PTT is depressed)
Pin 2 - PTT Switch 2
Pin 3 - Mic Audio
Pin 4 - Ground

I have a datasheet / manual for these mics buried somewhere, let me know if you need it 

[dc8flightdeck]

Your description should work fine. Thats fantastic info!

It appears to me I can use the PTT pins to close the mute circuit on the speakers. Since that is (I assume) a DC circuit I think I will added a relay to it and use the relay to send a keyboard command via the Hagstrom KE108 so that the PilotEdge connection transmits whenever the mic is depressed.

Ill test it with a meter but I assume the speaker mute pins connect to the 28v DC circuit to toggle the relay thats located inside the speaker unit. Im making this assumption without having the chance yet to double check the schematic.

Do you have any of this equipment operational in a simulator?

Justin

[dc8flightdeck]

Im slowley getting the sytem installed and am testing each componant as I go. In regards to the mute function, connecting the two mute wires together has no effect, but placing either wire to the 28vDC ground makes the mute relay energize and it functions properly.

Today I tested the FO mike, speaker, and the computer Pilot Edge audio. It works very well. I also tested a 28v relay  that I placed between the mute output from the hand mic and 28v+. When the Mic is keyed it also triggers my relay. Tomorrow I connect the relay to a KE108 so it will send a transmit command to Pilot Edge, then I will be ready to call ground and see how the hand mic/overhead speaker works over the internet.

On a side note, installing two speakers and three hand mics to an intercom sure consumes a lot of wire!

[mickc]

Sounds like you are having a win then !

I didn't make it too clear in my earlier post, one of the mute wires is grounded all the time, then the other mute wire is connected to it to activate the mute relay.
When I said on the 737 pin 7 is grounded, i meant you will need to ground pin 7 also. ]
I have seen this done both at the ACP and also a short jumper wire at the speaker unit plug that bridges pins 6 and 7

[dc8flightdeck]

Interesting. I couldnt tell any difference when I tried both wires so I only used pin 7 (to pin 6) which worked well. One speaker connecter is missing the pin 3 wire so Im happy it works without pin 3.

[dc8flightdeck]

Today we tested the intercom hand mic and overhead speaker system with PilotEdge. I called Las Vegas Ground and he was kind enough to give me feedback on the three hand mics as I tested the system.



At the end he summed up the quality of the system by saying "When talking to flying airliners, United aircraft have a unique background hum when they transmit that no other airliner makes. Your transmission sounds exactly like that." Now keep in mind, I logged in as Janet 224 and he no clue that the sim is actually themed United with actual United equipment in the cockpit.



So cockpit is so authentic that even the radio system sounds like United over the virtual air traffic control network! Thats just cool.



The intercom system works as follows;
•4 headset positions are installed inside the cockpit.
•1 Headset position is installed at the radome.
•The 6th headset position is used to interface to the two overhead speakers and the three hand mics.
•When the mics are depressed, 28v DC ground goes through the headset mics to the overhead speakers to mute the speakers which prevents audio feedback. It also closes a relay that sends a keyboard command via the KE108 keyboard emulator for PilotEdge to send a live transmission over the internet.
•The audio  going to and from the computer passes though the Music in/out jacks on the 6 port intercom

•The audio  going to and from the computer passes though the Music in/out jacks on the 6 port intercom

I did not incorporate the 737 audio panels because the panels are designed to mix audio channels from multiple radios. Flight simulator doesnt support multiple audio channels for each of the com and nav sounds(radios).

If the 737 audio panels were the style that has on/off toggle switches then I could use those to toggle the FSX com and nav sounds that FSX mixes into its single com audio channel output. Of course that would an involved project.


Justin

[mickc]

Looks great Justin!