HH
LECTROSONICS, INC.
4
Pilot Tone Squelch
The benefit of the pilot tone squelch system is that the
associated receiver will remain muted until it receives
the pilot tone from the matching transmitter, even if a
strong RF signal is present on the carrier frequency of
the system. All Digital Hybrid transmitters use one of
256 different ultrasonic tones between 25 and 32 kHz
to operate the receiver squelch. The pilot tone frequen-
cy is chosen according to which of the 256 channels
has been selected by the frequency switch setting.
This ensures that all transmitters in a multi-channel
system have different pilot tone frequencies so that
even spurious RF from the wrong transmitters will not
open the receiver squelch.
Input Gain Range and Limiter
45 dB range of input gain adjustment allows gain
settings to accurately match the user’s voice and the
varying sensitivity of different microphone capsules. A
DSP-controlled analog audio limiter is employed be-
fore the A-D converter. The limiter has a range of more
than 30 dB for excellent overload protection. A dual re-
lease envelope makes the limiter acoustically transpar-
ent while maintaining low distortion. It can be thought
of as two limiters in series, a fast attack and release
limiter followed by a slow attack and release limiter.
The limiter recovers quickly from brief transients, with
no audible side effects, and also recovers slowly from
sustained high levels to keep audio distortion low while
preserving short term dynamics.
Long Battery Life
Switching power supplies throughout the design allow
over 5 hours of operation using two alkaline AA bat-
teries. Lithium batteries will provide over 8 hours of
operation. The battery compartment and contacts are
designed to prevent “rattle” as the unit is handled.
Menu-Driven Control
A high-resolution LCD and control panel with mem-
brane switches provide access to the menu-driven
setup. Transmitter RF power, high-pass filter, frequency
selection, backlight timeout, mute or talkback functions
and tuning modes are easily accessed.
Frequency Selection
Operating frequency is normally selected using a
receiver or analyzer to assess signals in the local en-
vironment to avoid interference. Once an interference-
free frequency is identified, the transmitter frequency is
set to match the receiver.
The LCD on the transmitter displays frequency in MHz
and with a two character hex code that is used on
most Lectrosonics receivers.
Membrane switches on the control panel select 256
frequencies in 100 kHz steps or 1024 frequencies in
25 kHz steps over a 25.6 MHz range.
Output Isolator
The output circuit includes a special RF device called
an
isolator
. Its purpose is to block radio signals from
coming back into the transmitter final amplifier through
the antenna.
The isolator suppresses IM (intermodulation) that
can take place between two or more transmitters that
are in close proximity to one another (a few feet).This
form of IM is a particular concern in stage produc-
tions where the transmitters must operate very close
together. Isolators allow the use of higher transmitter
output power without sacrificing IM rejection.
Isolators are rarely found in wireless microphone
transmitters due to the high cost, but they are the best
solution to address multi-channel IM between multiple
transmitters.
Antenna
A newly designed helical antenna allows the mic to be
held in any position, since the user’s hands have little
or no effect on the radiated power.
Microphone Capsules
The HH handheld transmitter is available from Lectro-
sonics with the HHC and HHVMC cardioid condenser
capsules. Capsules from several other manufacturers
are also available for use with the HH: those with a
1.25” x 28 thread pitch and three contact rings. Con-
denser or dynamic microphone heads can be used
with the HH, depending on the user’s preference or the
application.
IR (infrared) Sync
An IR Sync Port (enabled with firmware v2.10) is used
for quick setup with receivers that offer this feature.
Settings for frequency, step size and compatibility
mode are transferred from receiver to transmitter via
the IR ports.
Side Button Functions
A programmable switch on the side of the housing can
be configured as a mute or cough switch, to provide a
talkback, a power switch, or be disabled.
The talkback function provides a communication
channel when used with a receiver equipped with this
function, such as a Venue Wideband receiver with
firmware Ver. 5.2 or higher. When pressed and held in,
the side switch re-directs the audio output to a different
audio channel on the receiver. As soon as the switch
is released, audio is returned to the program channel.
The talkback function works only in the Digital Hybrid
compatibility mode.
See page 10 for details.
