When only one channel is used, an inflated barrier rises up from the bottom to prevent water from entering the unused channel.

Radios scan all available channels in the system to find an unused channel for a conversation.

At this point, the biggest barrier to launching a new cable station is the shortage of unused channels.

A new call can only be connected by an unused channel.

First you tune the radio to an unused channel, which is not always easy in urban areas.

Instead I coolly assessed my resources-and almost at once stumbled into an unused channel, here within my own self-field.

His flesh sword struck up into her channel, tearing and rupturing at the first, then expanding an unused but well-designed channel.

This raises important political questions as to why people do not have the right to broadcast on unused channels.

We suggest for political and technical reasons that you pick one of the unused channels in your area to begin experimenting.

Elsewhere, the extra megahertz might be eked out from unused channels.