Instruction: Extract information from the supporting document to answer the given question.

Input:
Question: Will this work with a cordless telephone and a headset attached to the telephone?
Document: The device is now hooked up, but there's no dial tone and an error message from the cordless phone saying that there's a telephone line failure. Unplugging the device restores order. Stalemate again. I sense a return coming on.
Does not work very well. I would not purchase again. Problem with hearing when this is attached to the phone.
Radio Shack's telephone/record connector has a 2.5mm jack, and needed a converter for my 3.5mm Olympus DS-61recorder. This one connects directly and seems to give less noise. If using with a Plantronics headset amp, remember to connect it between the phone and the device, not between the device and the headset.
Be careful - if you have a cordless phone and want to use this between the base station and wall jack - this will not work! I wish the description made that clear. this only works on a corded handset phone.
This product is complete garbage. It does not work with standard telephone cable for digital phones such as V-Tech. The hole on the adapter for the phone cable is much to small to accept it. Complete waste of money. Save yours!
I have not been able to use the product because the phone jack it comes with is RJ22 rather than RJ11. I can see how for people with standard Bell telephones, this would work perfectly, but my telephones are cordless, and I have to connect to a wall jack in another room. I have not been able to find an RJ11->RJ22 adapter online. So, this product is useless to me as shipped.
I did some fiddling with my headset to increase the microphone volume and viola, it now works. Also, I was having some trouble getting the audio to work through the microphone jack on my laptop. The adapter has a 3.5mm mono plug and I had to pull the plug out slightly to get a connection. I have ordered a 3.5mm mono female to 3.5mm stereo male adapter. We'll see if this fixes things.
Worked well for its intended purpose, no background noise noticed. It connects to the headset cord and must be used with a corded phone. I had to purchase a phone just to use it.
This interface plugs into the same jack as the headset and not the main line. At first this was confusing. However, once I figured that out all went well. The sound quality was as good as the phone receiver and it was easy to use with my laptop computer. For the cost, this was an unbeatable solution to the problem of recording meetings in an efficent and easy way.
This device was purchased to assist in direct connect for telephone recording. I was told by my investigator it was great tool.
Answer: I believe that it will NOT work with that setup. This device plugs into where the corded handset would normally plug into the base. It is not designed to work between the base and the wall. So I do not believe that this will work with a cordless phone. I could be mistaken about that. However, I am reasonably certain that it will only work with a corded phone that allows for unplugging the handset from the base. (Which also means that it won't work with some cheap corded models either.)