I purchased a headset that has a 2.5mm plug. The phone base that I need to use requires a standard modular telephone cord. Does anyone know if there is an adapter that can do this? If so where can I buy one. Thanks

Hi, and thank you for choosing IMShopping!

I'm not sure there are adapters that you can use to avoid using  a modular telephone cord, but there are wireless telephone systems that you use when you need a phone jack, but you don't have one available.

Home Depot has the GE Instajack Wireless Phone Jack System for $67.19.  Here is a little about this system:

Eliminates the need to run additional phone lines. No expensive hook up fees, no cutting or drilling walls, no tools required. Goes with you when you move. Includes base unit, extension unit and 6 foot phone line cord.  You can use with dial - up internet.

• Eliminates the need to run additional phone lines
• No cutting or drilling necessary
• Easily relocated, moves room to room.
• Caller ID compatible.
• MFG Brand Name : GE
• MFG Model # : 86597004
• MFG Part # : 86597004

Best Buy also has the RCA Wireless Phone Jack available.  Here is some about this one:

• Turns any AC outlet into a phone jack
• Wireless connectivity allows you to connect your phone to the Internet for VoIP calling (requires VoIP decoder box and VoIP subscription, not included)
• Also allows phone line access for satellite and TiVo® services (additional fees may apply)

I recommend these products because GE and RCA are very good brands, and Best Buy and Home Depot are very good stores.

I hope these suggestions are what you are looking for.  If you have more questions, ask IMShopping!