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3rd party microphones for Cisco Telepresence

I am looking for someone who has experience with 3rd party microphones in combination with Cisco Telepresence products. In my case is it a SX20 with mini Jack audio input and there I plan to use a XLS to Mini-JACK converter and than either two Cisco CTS-MIC-CLNG= Ceiling Microphone or two 3rd party microphones as alternative. Our customer is not happy with CTS-MIC-CLNG= because of its dimension.

I would need a 3rd party microphone for hanging ceiling supension with 360° opening angle.

21 Replies 21

Haydn von Imhof

I have done this a lot for C20 systems.

You will need a XLR to 4Pin mini Jack converter due to the C20 Pin outs which is the same on the SX20.

If you use a normal 3 pin mini jack you will get voltage across your ground pin from the Control voltage that powers the LED on the original Mic.

So if you user a 4pin minijack to XLR you only connect the Ground, Audio Hot and Audio-Cold.

C20 Microphone

Thank you for this information!


If you need more information email or video call me on

Hi Haydn,

Great info.  I'm curious if you were able to find these XLR to 4 pole 3.5 adapter cables anywhere for sale, or if you are custom making them for your jobs?



SX10 Mic In External Signal 

Audio Signal is Tip & Ring 1 

Audio wont pass unless 100 R + 360 R resistors are connected between Ring 2 & Sleeve 




i tried to Connect an non Cisco Mic to the Webex Pro Codec.

Mic worked good.


Now i like to use the Mute / Unmute function.

With the 360R + 100R Resistor circuit only unmute worked.


The resistor from the original Mic has 24k. When the button is pressed 560.

I tried it with these two resistors --> nothing happend.


Any Ideas how i can solve it.


I cant change the Mic's (thay are installed in the table).


Alexandra, in my particular case, I made an adapter using a 3 pole minijack (since I couldn´t find a 4 pole one); but considering pin-out of the minijack and the cannon connector (XLR) it worked fine. I used a C20 with two ceiling mic.

The same thing (regarding dimension) happened. I just took the MIC out of the huge acrylic (cuting the seal) and hunged the tiny MIC from the celing of the room. We have made a lot of tests, wiht and without the acryclic to hear the differences, but there wasn´t any.  The room was a reglar reunion room (15 meters by 4 meters and 3 meters high). The ceiling mic with the acrylic is four auditorims, with very tall roof. Hope it helps.

marianofarre, how did you use a 3 pole minijack? Wouldn't the ground and the mic control be shorted?

Hi Darren,

Since the Ceiling MICs don´t have MUTE Control Button, it was not a problem. GND and Microphone Control may be shorted, but they are signals not Voltage, so no QuickSet C20 damage were caused nor MIC was muted due to this.  I have two MICs connected con the C20 using this "home made adapter - XLR to miniplug 3-pole" and it is used quite often without any problem.

Regards. Mariano.

Hi Mariano

Can you explane, how you were able to provide the Ceiling MIC with the needed phantom power without using the Mic-Control-Pin?

I´m asking, because I do not get any DC voltage between Mic+ and GND or Mic- and GND.

I only do get about 10-11V between Mic control and GND, which could be used for powering the mic.



This was a while ago, and the "adapter" was made for a client (which I can not longer review the pin out and how it was made, unfortunatelly).

At that time, I found out that I needed an external power, but it happened to happen that worked the way it was built and no problems at all since then. There isn´t any external power. Just used the femate XLR connector and o the other end the 3-pole mini jack.

Maybe, with that small ammount of voltage is enough. The sound is very loud and clear on the other site of the videoconference.

Technical Specification of the Ceiling MIC stats that 12V to 48V is needed, dough:

Transducer: Electret Condenser

Impedance: 240 Ohms

Open-Circuit Sensitivity: 7mV/Pa (-43dB re 1V/Pa)

Power Sensitivity: -43dB re 1mW/Pa

Equivalent Noise Level: 20dB SPL typical (0dB=.0002 dyne/cm2), A weighted

S/N ratio: 74dB minimum at 94dB SPL

Maximum SPL at 3% THD: 150 dB SPL

Operating Voltage: 12 to 48 VDC Phantom power with positive voltage on pins 2 and 3 with

respect to pin 1 of output connector

Current Drain: 1.1mA

Switch: Frequency select switch for flat or rising response

Output Connector: Standard Male 3-pin XLR

Sorry not to be so explicit; but trustme it works fine!



thanks, I will test this with the same cabling and the ceiling mic.



Hi there,

we used also in the past for C20 a 3-pole minijack to XLR adapter to connect old MXP microphones to C20.

This worked great so far, but doesnt seems to work with SX20 at all. When connecting this 3-pole adapter to SX20 Mic Input someting seems to be shorted and this Mic Input gets totally muted until reboot without any plugged adapters.

It really seems there is a difference between C20 and SX20, can somebody confirm?

The adapters were selfmade by a 3rd company, so what is the working solution to build this adapter?



Hi Thomas

SX20 does not provide phantom power on audio hot/cold. C20 does. So you will need an external phantom power supply. To prevent the unwanted mic mute, I would recommend to use a 4pin 3,5mm connector, because with a 3pin connector, you would shorten 10V on Ring2 against ground.

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