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Appendix E
Optional Transponder
The transponder is an optional component of the MMP.
When installed, it allows
personnel on a research vessel to verify that the system is profiling as scheduled. This is
accomplished with a transponder deck unit that can measure the range to the MMP as it changes
over time. The transponder is driven by its own electronics and powered by eight 9 V alkaline
batteries. The alkaline transponder batteries are located in the controller housing (all eight of the
batteries must be installed for the transponder to function). The transponder draws no power
from the main lithium battery. Its average current drain is 3 mA, which will exhaust the alkaline
batteries in approximately one year.
NOTE
There is an “on/off” switch located on the transponder electronics boards (on a corner of the top
circuit board near the end cap of the controller housing). The switch must be in the ON position
for the transponder to function.
Disabling the electronics stops the loud pinging that can occur during bench testing. The
transponder can also be disabled by disconnecting all eight of the 9 V alkaline batteries. This
should be done by disconnecting the two in-line connectors in the wiring harness, leaving the
batteries in place. If the batteries are removed the ballast weights must be adjusted before
deploying the profiler (see Chapter 5, “Operations” for more information about ballasting the
MMP).
Note that the transponder utility tests only the transmit circuitry of the transponder. The
receive circuitry and the ability of the unit to function as a transponder can be tested with a deck
unit. This should be a regular part of system testing.
The transponder is largely autonomous, pinging in response to external acoustic signals
that fall in a 0.5 KHz band centered on 9.5 KHz.
A 6 switch DIP on the transponder electronics board is used to set the receive and
transmit frequency bands. Each band is 0.5 KHz wide and identified by its center frequency.
9.5 KHz is the default receive frequency. The transponder can be set to receive at 13.0 KHz
instead by changing the state of switch 5 from CLOSED (Logic 0) to OPEN (Logic 1).
Switches 1 (LSB) to 4 (MSB) control the transmit frequency: 0000 selects 7.5 KHz, 0001 selects
Appendix E-1