Voice Communications
Both hard-wired (cable) and through-water electronic voice communications systems may be used with surface supplied diving. Wired systems are more popular as there is a physical connection to the diver for gas supply in any case, and adding a cable does not make the system any different to handle. Wired communications systems are still more reliable and simpler to maintain than through-water systems. The communications equipment is relatively straightforward and may be of the two-wire or four-wire type. Two wire systems use the same wires for surface to diver and diver to surface messages, whereas four wire systems allow the diver's messages and the surface operator's messages to use separate wire pairs.
A standard arrangement with wired diver communications is to have the diver's side normally on, so that the surface team can hear anything from the diver at all times except when the surface is sending a message. This is considered an important safety feature, as the surface team can monitor the diver's breathing sounds, which can give early warning of problems developing, and confirms that the diver is alive.
Divers breathing helium may need a decoder system which reduces the frequency of the sound to make it more intelligible.
Through water communications systems are more suitable for scuba as the diver is not encumbered by a communications cable, but they can be fitted to surface supplied equipment if desired. Most through water systems have a Push To Talk (PTT) system, so that high power is only used to transmit the signal when the diver has something to say. For commercial diving applications this is a disadvantage, in that the supervisor can not monitor the condition of the divers by hearing them breathe.
Dry bells may have a through water communication system fitted as a backup.
Read more about this topic: Diver Communications
Famous quotes containing the word voice:
““Pray my dear,” quoth my mother, “have you not forgot to wind up the clock?”M”Good G—!” cried my father, making an exclamation, but taking care to moderate his voice at the same time,—”Did ever woman, since the creation of the world, interrupt a man with such a silly question?””
—Laurence Sterne (1713–1768)