RFC RX1600 Installation And Operation Manual page 17

DIGITAL CODE SQUELCH FUNCTION
Radiofrequency receivers tend to generate audio noise when they are not
receiving any signal. For this reason, the receiver must include a circuit
(called "squelch") to silence the audio output when the transmitter signal
is absent, in order to prevent undesired effects and serious risks of damage
to audio systems.
In traditional systems, a circuit verifies the presence of the radiofrequency
signal (at the receiver input) and mutes the audio output if the signal goes
below a predetermined threshold.
Interfering signals generated by television transmitters, radio broadcasting,
electricalappliances,computers,etc..areanothercauseofnoiseandcanactivate
the receiver, especially when the respective transmitter is switched off.
In the condition of strong interfering signals, as occurs when several
radiomicrophones are used simultaneously, the squelch threshold must
be set to the maximum value (minimum sensitivity of the receiver), thus
reducing the radiomicrophone's field of action.
Digital Code Squelch is the innovation that resolves this problem,providing
an improvement over the typical squelch techniques (i.e.the so-called"pilot
tone"). A coded digital signal is transmitted in addition to the audio signal
as sub-carrier. Each carrier frequency is coded, allowing the receiver to
recognise the presence of the transmitter tuned to the same channel and
to be silent in the event that the expected code is not received correctly.
This prevents a receiver from "opening" due to interferences when the
respective transmitter is switched off or at its range limit.
Main benefits of the Digital Code Squelch function:
• The transmitter can be switched off without worrying about whether
other transmitters or interfering sources are in the receiver's field.
• The transmitter can be switched on and off without causing annoying
noises ("pops"), thus making the presence of a MUTE switch on the
transmitter unnecessary.
BATTERY LOW FUNCTION
Transmitters normally have a LED to indicate low / empty batteries.
In the series RCF 1600,this indication is also present on the receiver (Battery
Low LED on the front panel).
17