Zoom X5V User Manual page 83

When I start to dial, I sometimes forget whether I'm dialing
over the PSTN or over the Internet (VoIP).
The X5v has a distinctive, lower-pitched dial tone when it is in
VoIP mode, compared to the standard phone dial tone for your
country. If you do not notice the X5v's change in dial tone after
you press # to begin a VoIP call, we recommend that you change
your VoIP dial tone to make it more easily recognizable. See page
34 for help changing your ring tones.
Sometimes it's hard to understand people on VoIP calls.
If you are making or receiving VoIP calls during a period when
there is very heavy Internet traffic, you may notice an effect on
voice quality. For example, you may encounter a delay in hearing
the other person talk, or there may be brief intervals where it's
difficult to understand what the other person is saying. Sometimes
this is unavoidable. Your service or some other connecting link
between you and the person you are calling may become
congested. If someone is using the ADSL line to download or
upload large files—music or video files, for example—while you
are on the phone, it may affect voice quality. You may want to
avoid this situation.
Appendix D: Troubleshooting 83