Subspace isolation field

A subspace isolation field (or subspace force field) is a localized force field that contains its own pocket of subspace.

In 2368, most of the command crew of the USS Enterprise (NCC-1701-D) were able to use a subspace force field, in conjuction with a phase discriminator, to phase-shift themselves into the time continuum of the Devidians, aliens who were using a synchronic distortion with a positive displacement of .004 percent to conceal themselves. 

The next year, Captain Picard suggested the use of subspace force fields to beam on board the Enterprise, which was trapped in a temporal fragment. Geordi La Forge agreed but noted that they needed an extremely sensitive phase discriminator for the plan to succeed. On the advice of Lieutenant Commander Data, they used the emergency transporter armbands, which contained a sufficiently powerful discriminator. La Forge modified several armbands for use by the away team, enabling them to exist and interact in the fragment without being integrated into it's timeframe, essentially creating an artificial pocket of time around each member of the away team.