If switches are to be used within the chamber environment, select and use
only intrinsically safe switches which do not cause an arc when making or
All amplifiers, switching units, and volume controls will be outside the
chamber. Amplifiers should be selected so as to normally operate using 110
VAC and alternately capable of working on the emergency power.
5. EXAMPLE INSTALLATION. A simple audio system installation is shown
schematically in Figure 10-2. The system is arranged with independent
sending and receiving channels for continuous two-way communication. As an
alternative, "press to talk" switching can be adopted with some economy in
wiring and amplifier requirements. If switching is used, it is essential
that the occupant-to-outside channel always be open when all switches are
released. Telephone-type transceivers can be substituted for one or more of
the headsets. A tape recorder can be provided to record crew-to-monitor
conversations, if desired. The system as shown will not function as an
intercom for the crew, but can be modified to do so. Crew members wearing
the headsets will have artificially improved acoustics in that they will be
isolated from chamber echoes.
monitoring by means of closed-circuit television adds one of the most
valuable tools in the safe monitoring of chamber occupants and can add
considerably to the efficiency of chamber operations. It also provides a
basis for maintaining a visual record of experiments on videotape at an
average cost far below film recording. This section covers some aspects of
video communications useful as background information for the hyperbaric
VIDEO COMMUNICATION AS A SUPPLEMENT TO DIRECT OBSERVATION. Video
communication should not be considered a total replacement for viewports.
Viewports are a necessity because of their nearly 100 percent reliability and
inherent ability to permit stereoscopic, high-resolution viewing in perfect
color. It is also psychologically desirable to give the chamber crew a
direct window to the outside world. Television communication does, however,
offer several advantages for long-term observation tasks:
The chamber can be observed by several people located at a control
console remote from the chamber itself.
By use of 300 M and wide angle lenses and an interior panning
camera, a greater variety of observations can be performed than would be
possible through a viewport.
Long-term observation can be made with less fatigue to the
Both visual and voice monitoring can be performed at a common
location adjacent to the chamber operating controls.