Cortelco phones working with Audiocodes MP1288

[chrisk35]

Hello,  

We recently installed multiple MP1288s in our environment.  We have a large number of Cortelco 255400VBA-20M phones spread throughout our campus.  Currently we are experiencing an issue where the phones do not ring loud enough to be heard.  The sound is a muffled clicking.  I have found that when you slide the volume adjuster to the halfway point on the phones, they can be heard but not loud enough for most areas.  I am currently troubleshooting this issue with an Audiocodes tech, but still have not figured out a way to get the volume of the bell loud enough.  Has anyone ever come across this problem?  

I have checked the firmware.  We have attempted to change the Trapezoid Ring Parameter, to no avail.  Any help would be appreciated. 

[Eliot]

hi @chrisk35 

These documents may help in troubleshooting the ring volume issue.

Zoom support article describing how to set up your MP1288 on Zoom Phone.

Quick start guide for the AudioCodes MP1288

Coretelco Datasheet specifies ring voltage, ring frequency, maximum ringer load, and distinctive ringing.  Datasheet specifies “Ringer Equivalency Number (REN) 3.”  Check the number of Cortelco phones connected to each FXS port multiplied by the REN of each phone to be sure the result does not exceed REN of 3.

MediaPack 1288 - High-Density Analog Gateway Datasheet

User’s Manual pages 818 -819 cover AnalogCoefficientTypes.  You should probably set this to “USA”.

MP-1288 High-Density Analog Media Gateway User's Manual Version 7.2

Cortelco manual provides information on setting ringer volume control.  Try setting ringer volume to high. 

Cortelco states “The REN for this product is part of the product identifier (label on the bottom of the telephone) that has the format US:AAAEQ##TXXXX. The digits represented by ## are the REN without a decimal point (e.g., 05 is a REN of 0.5).”

2500_2554_manual.pdf

Did my response answer your question? If so, please don't forget to mark the reply as an accepted solution.

thanks,  eliot

[chrisk35]

Hi Eliot,

Thank you for your response.  I verified that we do not exceed a REN of 3 on any of our FXS ports.  I also verified that the Analog Coefficient Type is indeed set to USA. 

One of the main issues is that we do not hear an audible ring unless the ringer volume arm is about halfway between off and loud.  If you change this at all, you only get a clicking sound on the device.  Currently we have about 400 of these Cortelco phones across our campus.  We have them on multiple MP1288s.  We migrated from Avaya gateways which never had this issue.  Thank you for any other ideas or troubleshooting tips you may have. 

Chris 

[Eliot]

hi @chrisk35 

I suggest getting in touch with your AudioCodes distributor/partner for troubleshooting assistance.

AudioCodes suggests “Customers without direct support agreement (CHAMPS), for any support-related issues, please contact the AudioCodes distributor (partner) from whom you purchased your AudioCodes product from.”

Support and Maintenance | AudioCodes

According Zoom Phone Certified Hardware, these AudioCodes MP1288 are Zoom certified but are End of Life (EOL) as of 6/1/2022.  Zoom shows two certified firmware download links (Long Term Support (LTS) and Latest Release (LR) as follows:

7.40A.600.231 (LR) (9/14/2025) 7.40A.501.871 (LTS) (9/14/2025) (Manual upgrade only)

Which firmware are you using?

Zoom Phone Certified Hardware

In the meantime, you might test one Cortelco desk phone connected physically close to one FXS port on the mp1288.  If the phone rings properly, maybe the issue at distant locations is signal loss caused by distance and wire gauge.   Maybe there is a mp1288 setting involving distance support.

According to audiocodes, mp1288 supports either sinewave or trapezoid ringing:

Ring Voltage –

54 Vrms Sinewave balanced ringing of up to 288 phones simultaneously –

85 Vrms/20Hz – Trapezoid waveform ringing of up to 6 phones per each 12 ports segment

Notes: Balanced ringing only, enables simultaneous ringing of 288 phones (72 per FXS blade given REN3 load)

You might use an AC voltmeter to measure the ring voltage at the Cortelco phones in the field against mp1288 specified voltage.  You might also check how the Cortelco ring volume adjustment affects the ring voltage.

Since these phones worked with Avaya gateways, it might be helpful to see what FXS parameters were set such as ring voltage and waveform.  What model Avaya gateways were previously used?

Sorry, I can not be more helpful.

Did my response answer your question? If so, please don't forget to mark the reply as an accepted solution.

Thanks,  eliot