Firecom MR-55X Cable

salberd · Post by **salberd** » Thu Mar 15, 2007 8:52 am

I am looking for the schematic for the Firecom MR-55X.

It connects the Kenwood TK-890 to teh Firecom 210 intercom system.

Thanks for any help you can give!!!

BDB · Post by **BDB** » Fri Mar 16, 2007 4:21 am

On the firecom site you can download MR Lookup Guide.pdf and this file has the schematic you are looking for. If you cannot find it there PM me your email and I'll send it to you.

salberd · Post by **salberd** » Fri Mar 16, 2007 7:17 am

Thanks!

I guess it helps to goto to the next page.

I closed the file when I seen it was $180.00 and posted here...lol

Thanks for your help and quick response!!!!

chipjumper · Post by **chipjumper** » Fri Mar 16, 2007 4:00 pm

Yeah I noticed that the MR-1X (Spectra) interface cable is $180 too. Is it necessary to used their interface box since I have the schematic? Could I just sacrifice an old mic cord and broken head?

Will · Post by **Will** » Fri Mar 16, 2007 11:16 pm

I can't believe my eyes, $180 for a cable.......

On the Spectra interface cable Firecom shows. the radio volume affects the headset volume---dangerous in any PS application. Volume of the speaker should be independant of the headset volume.

Anyway I always use the 15 pin accy cable for intercom interfacing. One simple capacitor added to the Spectra and away you go.

No need to distroy a mic cable to use the Firecom unit.

BDB · Post by **BDB** » Sat Mar 17, 2007 5:16 am

If you have PTT on the rear option connector you can use the DB15. None of the spectras in my fleet (77) have PTT available on the DB15. My understanding is it is an SP option (jumper). If there is a quick fix without physically modifying the drawer I'm all ears. When using the MR1X you're getting palm mic functionality as well as intercom PTT. David Clark (what we use) uses the same interfacing for a spectra (thru the mic port) and thier interface box (40107G-01) is over $200.00 for just the box. In both the Firecom and David Clark systems speaker volume directly impacts radio volume in the system .

Will · Post by **Will** » Sun Mar 18, 2007 3:23 pm

BDB wrote:. When using the MR1X you're getting palm mic functionality as well as intercom PTT. .

What??? You get all the SAME functions using the 15 pin connector on the Spectra radio (Lo Pwr, second DB25 on the HiPwr).

All Spectras have PTT at pin 13. If the PTT is not on the 15 pin connector at pin 13, there is a missing jumper on the command board due to a SP option. This may be able to get around easally. Check for the Mic hi on your 15 pin connector, if that is there then we can do step two.

BDB · Post by **BDB** » Sun Mar 18, 2007 4:54 pm

Yes I know if you go in the back of the radio you still maintain mic functionality. I was elaborating on why the interface retails for $180.00. I have not had any luck getting PTT on the rear option connector on Pin 13 on the radios in my fleet (A9 spectras/ sys9000) and have always went back to using the mic interface.

chipjumper · Post by **chipjumper** » Sat Apr 07, 2007 6:44 am

Will wrote:Anyway I always use the 15 pin accy cable for intercom interfacing. One simple capacitor added to the Spectra and away you go.

Will, are you using the capacitor on the speaker hi wire to remedy any balancing?

This is what I've figured out in reference to the DB15:

Spkr Hi = Pin 6
Spkr Lo = Pin 7
Mic Lo = Ground
Mic Hi = Pin 15
PTT/HUB Ref = ????
PTT = Pin 13

Where is the PTT/HUB Ref? Is it the "Digital Ground Pin 8"???
(edit: Answer is yes - the Digital Ground is the PTT/HUB REF)

Will · Post by **Will** » Sun Apr 08, 2007 1:02 am

chipjumper wrote: Will, are you using the capacitor on the speaker hi wire to remedy any balancing?

NO.
I do not use the speaker output for intercom function.

Will · Post by **Will** » Thu Apr 12, 2007 12:19 am

I sent chipjumper a pinout for the Spectra to the Firecom. He will be using the second DB 25 connector on the remoted Spectra.