The audio bandwidth of S25 Reportophone in combination with a standard mobile phone is limited by the capacity of the GSM connection: 8 kHz sample rate / 8 bit. The quality is comparable with that of S20A Reportophone as it has the same kind of processing inside. Some people tell us it is even better than POTS.

More and more telephone companies are now offering "HD-voice" / G722.2 also known as AMR-WB ("Adaptive Multirate Wideband"). This system offers 8 kHz bandwidth and is currently available in a number of countries. Some broadcasters are already using it with very good results.
Most modern mobile telephones are equipped with this codec - certainly the more expensive ones - and the S25 Reportophone and EA916 journalist unit are supporting this also.

You can set up such a system with an S25 unit as a stationary hybrid or an EA916 Journalist unit with suitable mobile telephone in the studio.
The new Eela Audio EA816 GSM stationary hybrid is also supporting HD-Voice. Information about the EA816 can be found on www.eela.n/EA816

A list of available mobile telephones with AMR-WB codec can be found on wikipedia.

An updated  list of GSM networks supporting HD voice can be found on


New models of mobile telephones and Smartphone’s are introduced almost weekly. Most of the new models are based on the same internal hardware so interfacing stays the same. Nevertheless it is a challenge to keep up with those developments, the list of cables for the S25 and mobile phones is never complete. If in doubt or your model is not in the list please contact us. For the current list se the download pages of the Eela Audio website.

We found that there are different Nokia telephones using the same connector but with different wiring.
The 1100 series, 1600 series and HS47 series requires a slightly different cable than the older HDC5. With the standard HDC5 cable these telephones are not recognised by the S25 Reportophone. We do offer special cables for these telephones, for details see price list.
For many mobile phones it is relatively easy to make your own cable. You can contact us for a diagram for your telephone.

The Apple iPhone and iPad do have the same connector as the Nokia AV3,5-series but are wired differently.


Important information on NiMH batteries and built-in charger

Always discharge new or really empty batteries before use!
A full discharge / charging cycle will take between 7 - 8 hours for 2000 mAh batteries.
A full charge of 2000 mAh batteries as supplied will allow you the use of minimum of 10 hours.
(We have tested these with high level music on headphones for up to 18 hours)
New S25 Reportophones are shipped with 2700 mAh batteries.

How to get the most out of a set of rechargeable NiMH batteries:
Download pdf file here


Pictures how to disable the auto shut off function. The standard versions of the unit will shut off automatically if not active for approx. 10 minutes. The timer circuit will retrigger if the input level reaches a level between the 2 green LEDs of the level display. If the input level stays below that threshold for approx. 10 minutes the unit will shut down to preserve battery power.
You can disable this function by soldering 2 points together.

Also learn how to use the unit as a stationary hybrid (V2 only, SN > 0100).

Download the pdf file here.


The S25 is built with this in mind. The aluminium case is chromium plated on the inside and outside thus forming a Faraday cage.
When opening the unit, make sure that you re-establish the contact between the cover and base unit upon assembling. This is done with the 4 screws holding the top cover. Also the connectors on the back must have an electrical connection to the base unit.

The input electronics are specially designed to eliminate the typical radiation noise of the telephone. Always use a symmetric, screened signal cable for the microphone and make sure the screening is connected to pin 1 on both sides. We also found that there is a huge difference between various types of microphones. Popular reporter microphones like the Sennheiser MD21 or MD42 are good as well as the Beyer Dynamic M58 Reporter microphone.

Last update: October 2014



This information is not in the user manual!