Call quality was great. Though both the Z9 and the Z9i has Voice Isolation technology, the Z9i purports to have better sound. Indeed, we found it to be true. There are two modes to the voice-isolation sensor--Standard and Max. Standard allows for regular noise reduction and echo cancellation, but still retaining the sound of the natural voice, which is good for everyday use. The Max version is best for really noisy situations where the voice quality isn't as important as just the ability to hear the other person. We tested out the headset in a quiet office environment, and callers heard us loud and clear without any problems. There was still some static, but it wasn't a big deal. Next, we tested out the Max setting in a crowded restaurant setting, and though it was still a bit difficult to hear, it was certainly a lot clearer than without it. Callers had no problem hearing us at all, though they did say our voices sounded slightly more robotic in Max mode.
Other features of the Z9i include the typical answering, ending, and rejecting calls, plus last number redial, voice dialing support, call waiting, call conferencing, and the ability to transfer a call from the headset to the phone and vice versa. Also, the Z9i can pair up to five devices.
Rated talk time is 5.5 hours, and rated standby time is 8.3 days.