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How to interface a headset with XTL 2500

This forum is dedicated to helping people with questions about installing radio equipment in vehicles. This can include antenna installs, electrical wiring questions/problems, and mounting systems. Pictures of installs are welcome.

Note: Discussions regarding lighting, sirens, and other equipment now has its own forum in the 'off-topic' section below.

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cfd505
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Posts: 4
Joined: Wed May 20, 2015 8:07 am

How to interface a headset with XTL 2500

Postby cfd505 » Wed May 20, 2015 8:21 am

I'll state up front that I'm not a radio expert. I have done several straight-forward installs at our fire department, but I need some guidance on the setup for our new fire truck. We just ordered the truck and would like to have a PTT headset at the pump panel. We don't have the luxury of having dual-head radios, which would make things a little easier. We also don't have the extra room in our budget to have the truck manufacturer install a pump panel communications system (which they integrate with a cab intercom system - something we don't need or want).

What we are wanting to do is interface a Firecom PTT headset (like the UH-10) directly into the accessory port of our XTL 2500 mobile in the cab. (Again, the manufacturer of the truck is saying they'd have to run it through the Firecom intercom system with several modules before finally tying into the radio itself. I don't believe this.) I can get my hands on a Firecom PP-20 weatherproof jack that's designed for use on a fire truck pump panel. It is a 5-conductor jack for use with their 5-conductor plug headsets. The PP-20 has a long run of flat cable coming out of it that ends with a RJ-12 plug.

Here is the pinout of the 5-conductor plug on the headset:
-Speaker High
-Speaker Lo
-Mic High
-Mic Low
-PTT

My question is this: given the pinout shown above, how would I connect this to the accessory port on the XTL 2500? Can it be done? Which wires would be connected and to what? This is the part I'm unsure about. I would have no problems doing the actual installation of this once I figure out what connects to what. I would appreciate any and all help.

Jim202
Posts: 3483
Joined: Sun Sep 09, 2001 4:00 pm

Re: How to interface a headset with XTL 2500

Postby Jim202 » Wed May 20, 2015 1:35 pm

cfd505 wrote:I'll state up front that I'm not a radio expert. I have done several straight-forward installs at our fire department, but I need some guidance on the setup for our new fire truck. We just ordered the truck and would like to have a PTT headset at the pump panel. We don't have the luxury of having dual-head radios, which would make things a little easier. We also don't have the extra room in our budget to have the truck manufacturer install a pump panel communications system (which they integrate with a cab intercom system - something we don't need or want).

What we are wanting to do is interface a Firecom PTT headset (like the UH-10) directly into the accessory port of our XTL 2500 mobile in the cab. (Again, the manufacturer of the truck is saying they'd have to run it through the Firecom intercom system with several modules before finally tying into the radio itself. I don't believe this.) I can get my hands on a Firecom PP-20 weatherproof jack that's designed for use on a fire truck pump panel. It is a 5-conductor jack for use with their 5-conductor plug headsets. The PP-20 has a long run of flat cable coming out of it that ends with a RJ-12 plug.

Here is the pinout of the 5-conductor plug on the headset:
-Speaker High
-Speaker Lo
-Mic High
-Mic Low
-PTT

My question is this: given the pinout shown above, how would I connect this to the accessory port on the XTL 2500? Can it be done? Which wires would be connected and to what? This is the part I'm unsure about. I would have no problems doing the actual installation of this once I figure out what connects to what. I would appreciate any and all help.


If you go to the batlabs.com site or the repeater builder site, I believe the accessory pin connections are given.

What you didn't say is what power level the radio is. If it is a low or medium power, the accessory connector is a special Motorola connector that you can buy or use the existing one. Generally it also provides the speaker connections and the ignition power feed wire. You will need the special pins this connector uses. Don't make a mistake putting the pins in, as you will also need the special extractor tool to get them out. Also you will need the crimper tool to crimp wires onto the pins before you insert them into the accessory connector. If I remember the package you order from Motorola for the pins is for 10 pins.

If you have a high power radio there is no accessory connector on the rear of the radio. On the front you will see a DB25 female connector. This is the accessory connector.

Now some important points to remember. You can't ground either side of the speaker wires. YOU WILL BLOW THE AUDIO OUTPUT AMP if you do.

There is a fixed level RX audio output available that could be used if there is an audio amp to bring the level up to what the headset requires. This line has a DC bias on it, so you can't run it into a transformer that feeds an audio amp.

The external mic hi on the accessory jack can be used for the mic input. There is a gain setting to crank up or down the gain as required. Changing the external mic gain has no effect on the control head mic gain. Again bear in mind there is a DC bias on this line. You might need to cap couple to this line if the mic source is a low impedance. Another point about using the external mic input, you might have to go into the software and change a setting for the source. There is only 2 selections. If one doesn't work, go to the other.

I will have to do some homework on the part numbers and where to find the software settings for the radio. Can't remember them off the top of my head right now.

Jim

cfd505
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Posts: 4
Joined: Wed May 20, 2015 8:07 am

Re: How to interface a headset with XTL 2500

Postby cfd505 » Wed May 20, 2015 2:48 pm

According to the information I obtained when I googled the model number, this is a 10-35W radio. The accessory connector is in the back and currently has the ignition sense, speaker + and -, emergency, and ground pins in the connector (although the emergency and ground pins apparently aren't connected to anything, as there are only the external speaker and ignition wires coming out).

This is the pinout that I found for the XTL 2500: http://communications.support/attachmen ... 1384483968

There are "AUX MIC" and "AUX PTT" pins on the accessory port. That's the only thing I saw on there that resembles the 5 wires I posted from the headset jack. I'm confused as to what would be connected and where. Would the "speaker high" and "speaker lo" just be wired into the same speaker wiring that goes to the external speaker in the cab (daisy chained)? What about the "mic high" and "mic low" from the headset? Are both of them connected to something or only one (if so, which one)?

cfd505
New User
Posts: 4
Joined: Wed May 20, 2015 8:07 am

Re: How to interface a headset with XTL 2500

Postby cfd505 » Wed May 20, 2015 3:07 pm

Also, I'm not dead set on the Firecom headset. I've read good things about the David Clark headsets, as well. I'm for whichever one will work and interface the easiest, although I do like the Firecom weatherproof pump panel connector.

cfd505
New User
Posts: 4
Joined: Wed May 20, 2015 8:07 am

Re: How to interface a headset with XTL 2500

Postby cfd505 » Wed May 20, 2015 3:35 pm

I just spoke with tech support at Firecom. The guy confirmed what the apparatus manufacturer said that there must be an interface between their headset and the mobile radio. He gave me the information about a radio interface that they sell that is not an intercom system. It is priced very reasonable and has an interface cable specifically for the XTL 2500, so I think we will just go that route and save the headaches of trying to piece it together without the interface.

Jim202
Posts: 3483
Joined: Sun Sep 09, 2001 4:00 pm

Re: How to interface a headset with XTL 2500

Postby Jim202 » Thu May 21, 2015 3:59 pm

cfd505 wrote:According to the information I obtained when I googled the model number, this is a 10-35W radio. The accessory connector is in the back and currently has the ignition sense, speaker + and -, emergency, and ground pins in the connector (although the emergency and ground pins apparently aren't connected to anything, as there are only the external speaker and ignition wires coming out).

This is the pinout that I found for the XTL 2500: http://communications.support/attachmen ... 1384483968

There are "AUX MIC" and "AUX PTT" pins on the accessory port. That's the only thing I saw on there that resembles the 5 wires I posted from the headset jack. I'm confused as to what would be connected and where. Would the "speaker high" and "speaker lo" just be wired into the same speaker wiring that goes to the external speaker in the cab (daisy chained)? What about the "mic high" and "mic low" from the headset? Are both of them connected to something or only one (if so, which one)?



OK, slow down just a bit.

The mic hi from hour headset would go to the Aux mic pin 23. Mic low would go to one of the ground pins 1 or 14.

The PTT from the headset would go to the aux PTT pin 16.

You need to find out about the audio RX level the headset requires. You also need to find out if either side of it is grounded. Again you DO NOT WANT TO GROUND EITHER SIDE of the speaker output wires coming from pins 20 and 26. You will blow out the speaker audio amp in the radio.

If you open up the accessory connector, you should find the emergency pin 15 goes to one of the ground pins 1 or 14.

The ignition control goes to pin 25.

As I said in my earlier post, if you don't need a high level audio RX input to the headset, you would be better off using pin 21. This is a fixed level RX audio that is not controlled by the control head volume control knob.

With all that said, I will make my comments again that there are DC voltages on both the RX filtered audio pin and the aux mic input pin. You might have to use a series capacitor to block the DC voltage so you don't cause a problem. I have found that using a 1.0 to a 2.2 uf capacitor generally works well. Put the + side of it towards the radio.

Back to my original post. I mentioned you will need some pins. The Motorola part number I have used in the past is 3980034F01. I can't remember if it's 10 pins per package or a larger number. You should check with MOL for that answer.

On the software side, you need to go to the advanced tab and make sure the selection is the "aux_mic.

In the radio configuration tab, go to the radio wide selection and under the external mic, uncheck all 3 of the AGC gain boxes. Then in the external mic you will see 23 audio gain settings. Here is where you can play with the external aux mic gain. This setting will depend on the audio output level of the headset mic. You might have to go as high as the +12 setting to get enough audio if the mic your using only provides a low output level. DO NOT CHANGE THE NORMAL MIC SETTINGS.

As always after making any changes to mic gain settings, do a radio check. If you can get the mic more than 3 or 4 inches away from your mouth and the mic audio has not dropped down in level, your gain setting is too high. It will bring up all the background noise and might cover what your saying in the headset mic. I always try to use a simplex or talk around channel to do any mic testing. That way I can use another radio and hear what is happening without relying on someone else that may not have a clue as to what is going on. Remember, feedback from other radios is what your trying to prevent.

Have a good time doing your modifications.

Jim


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