5
located in a diving bell or recompression chamber, the MK2-DCI can be used as
the communications link between the divers and the outside. When the system is
used where conditions are noisy, the tender can switch off the speaker and use a
headset and boom microphone. However, when using a headset with a boom mi-
crophone, the tender must use a push-to-talk (PTT) button to communicate. Our
headset with a boom microphone has a PTT button located on one side of the
headset. The MK2-DCI also has a PTT. The divers’ communication is the primary
signal. When the tender uses the PTT button, his signal becomes the primary sig-
nal. If the diver is trying to say something while the tender is talking, the tender
will not hear the diver until he releases the PTT button.
The divers’ helmets and/or full-face masks typically are wired with the earphones
and microphones tied together. When wired like this, the divers’ earphones and
microphones function together. Bubbles passing by the earphones while the diver
is talking will be picked up via the earphones, causing the communications to be
noisy. When the tender is talking to the diver, his voice is heard not only from the
diver’s earphone, but also from the microphone!
3.3
FOUR-WIRE MODE
The four-wire mode provides continuous open-line communications between the
tender and up to five divers, or any combination of recompression chambers or
diving bells. The four-wire mode will give you optimum performance and intelli-
gibility by the MK2-DCI. Using this method, everyone hears each other simulta-
neously. Therefore, the earphones, speakers, and microphones must be isolated to
prevent feedback. All earphones are connected in parallel. A four-wire cable is
required for all stations. Two of the wires are used for the microphone and two for
the headset(s) and earphone(s) (Fig. 3). The diver earphones should be connected
to the “EARPHONE” binding post on the surface unit (via the black banana plug
located in the 1 or 2 Diver sections). The banana plug on the tender’s OTS headset
should be connected to the “EARPHONE” banana plug (black; Tender section).
The remote plug on the headset should be connected to the “REM” receptacle
located in the Tender section. The tender’s microphone should be connected to
the red banana plug labeled “MICROPHONE” (Tender’s section). The diver’s
microphone should be connected to the “MICROPHONE” banana plug (red) in
the Diver’s setion of the MK2-DCI. When in the four-wire mode, everyone is on-
line together. It is similar to a telephone conference call.
NOTE: The “Diver Select” must be in the “BOTH” position for four-wire com-
munications in order to hear everyone. A headset with a boom microphone has
to be used by the tender when using the MK2-DCI in the four-wire mode. If you
experience feedback from the headset’s microphone, turn off the front panel
speaker.