Plantronics HIS Direct Cable – 72442-41
 
Compatible with: Specific Avaya Telephones
Understanding Direct Connect Cables vs. Amplifiers:
When using any H-series headset, a Direct Connect Cable or amplifier is required to plug in between your headset and phone.  Using a Direct Connect Cable will save you money versus an amplifier, but an amplifier will provide optimum sound quality and volume controls.
 
Direct Connect Cable:

Less expensive
Easy to install into headset port
Takes up virtually no desk space
Limited to use with compatible phones only (Your future phone may not be compatible and require an amplifier)
 
Amplifier:(Plantronics M22)

Compatible with most phones
Battery or AC powered to provide optimal sound quality
Speaker volume adjustment
Microphone volume adjustment (Key point that Direct Connect Cable doesn’t have)
Lifting handset with each call may be required, depending on your phone