Lectrosonics WM/E01, Instruction Manual

Page: 5 / 20

Watertight Transmitter
Rio Rancho, NM
5
Signal Encoding and Pilot Tone
In addition to controlling the limiter, the DSP also en-
codes the digitized audio from the A/D converter and
adds an ultrasonic pilot tone to control the squelch
in the receiver. A pilot tone squelch system provides a
reliable method of keeping a receiver output muted
(audio mute) even in the presence of significant
interference. When the system is operating in the hy-
brid mode, a different pilot tone frequency is generat-
ed for each carrier frequency to prevent inadvertent
squelch problems in multi-channel sytems.
Microprocessor Control
A microprocessor monitors user command inputs
from the control panel buttons and numerous other
internal signals. It works intimately with the DSP to
ensure the audio is encoded according to the se-
lected Compatibility Mode and that the correct pilot
tone is added to the encoded signal.
Compatibility Modes
WM/E01 transmitters are designed to operate with
Lectrosonics Digital Hybrid receivers and will yield
the best performance when doing so, however, due
to the flexibility of digital signal processing, they can
also operate with Lectrosonics Euro version IFB
receivers.
Control Panel
The control panel includes four membrane switches
and an LCD screen to adjust the operational settings.
Multi-color LEDs are used to indicate audio signal
levels for accurate gain adjustment and for battery
status.
Battery Operation
Switching power supplies convert regulated battery
voltages to operate various circuit stages with maxi-
mum efficiency. With the variety of alkaline, lithium
and rechargeable NiMH batteries available today in
the AA format, there are many choices to maximize
operating time or minimize cost as needed for any
application.
The firmware “remembers” the settings when the
batteries are exhausted. After new batteries are
installed, a quick press of the AUDIO and FREQ
buttons will turn the power back on and return to
the previous settings. This is a unique behavior that
takes place only when the batteries fail during opera-
tion. If the unit is turned off manually, a quick press
of the buttons will turn it on in the “standby” mode
instead.
Because the battery caps make contact with the
battery before the cap is seated, the power does not
turn back on automatically. This allows both batteries
to be installed and the caps tightened before power
is restored.
Frequency Blocks
Lectrosonics established a “block” numbering system
years ago to organize the range of frequencies avail-
able from the low end at 470 MHz band to the upper
end at 862 MHz. Each block includes 256 frequen-
cies in 100 kHz steps, which is the maximum switch-
ing range of the transmitters.
Circulator/Isolator
The RF output circuit includes a magnetically polar-
ized ferrite called an isolator that blocks RF sig-
nals entering the transmitter antenna from external
sources from traveling back into the final amplifier.
This greatly reduces RF intermodulation produced
when multiple transmitters are used in close proxim-
ity to one another (several feet apart). The isolator
also provides additional RF output stage protection
against static shock.