Great for Training: This telephone training adapter is great for landline phones with RJ9 headset jack. It can splitter into two listeners/callers same conversation simultaneous. Great suitable for business professional, call center, work from home or anywhere. Lightweight and Convenient: This telephone splitter is very lightweight and provides clear voice incoming and outgoing, the cord is 19.6 inches (50 cm) long. It helps with training and can also use as an extender. Easy to Use: Plug and play, can plug either into handset port or 4P4C RJ9 headset port. Allows the use of two headsets on one telephone. Allow you to setup that you can choose either handset or headset for your calls. Compatible Telephones: This RJ9 Y splitter is compatible with Plantronics, Mitel, Cisco, Yealink, Avaya, Polycom, ShoreTel, NEC, Aastra, Nortel, GE and other IP phones. Compatibility Notices: The compatibility of this telephone training adapter depends on whether your RJ9 headset is compatible with your telephone. As long as your headset is compatible with your telephone, the adapter will work properly.