RADIO RECEIVER OPERATIONAL CHECKING METHOD AND SYSTEM

METHODE ET SYSTEME POUR VERIFIER LE FONCTIONNEMENT D'UN RECEPTEUR RADIO

English Abstract

A clock-driven pulse source is used to apply repetitive short
pulses to the squelch control connection point of the squelch
circuitry of a radio receiver to deactivate momentarily the squelch
circuitry at regular intervals. This provides periodic noise bursts
of "de-squelch" pulses on an otherwise silent radio in order to
inform the radio operator that the radio is live and that the
volume is adequate. A light may also be connected to the system to
provide a second, visual, indicator of the operational status of
the radio.
This radio receiver operational checking system may also be
utilized where there are two or more radios in use by providing an
additional clock-driven pulse source for each radio in use. The
system may be arranged so that the status of individual radios may
be quickly ascertained by sound and/or by light indicators.

French Abstract

Une source d'impulsions pilotée par une horloge est utilisée pour appliquer de brèves impulsions répétitives au point de connexion utilisé pour la commande du circuit d'amortissement audio d'un récepteur radio afin de désactiver momentanément ce circuit à intervalles réguliers. Ceci produit des salves de bruit périodiques d'impulsions de «désactivation» dans le récepteur, lequel est par ailleurs silencieux, pour informer l'opérateur que le récepteur est en service et que le volume est adéquat. Un voyant peut également être connecté au système pour fournir une seconde indication, visuelle celle-ci, de la situation opérationnelle du récepteur. Ce système peut également vérifier le fonctionnement de plusieurs récepteurs radio en fournissant une source d'impulsions pilotée par une horloge à chacun de ces récepteurs. Il peut être installé de façon que la situation des récepteurs individuels puisse être déterminée rapidement au moyen d'indicateurs sonores et/ou lumineux.

Claims

CLAIMS
THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE PROPERTY OR
PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A radio receiver operational checking system comprising in combination:
a) a radio receiver including an active radio noise squelch circuit, set at
a level to eliminate ambient atmospheric and receiver noise when no radio signal is being
received, and including a squelch control connection point where said squelch circuit can
be disabled by the application of a voltage of appropriate magnitude,
b) a clock-driven pulse source for said radio receiver providing repetitive
short pulses for application to said squelch control connection point to deactivate
momentarily said noise squelch circuit at regular intervals to provide repetitive, short noise
pulses in the audio output of said radio receiver indicating that said radio receiver is
operational and awaiting a radio frequency signal.
2. The radio receiver operational checking system of Claim 1 further
comprising light indicating means for said radio receiver to monitor visually said audio
short noise pulse outputs of said receiver and to turn on when said short noise pulse
output of said receiver coincides with said short pulses from said clock-driven pulse
source being applied to said squelch control connection point of said radio receiver as an
indication of the operability of said receiver.
3. The radio receiver operational checking system of Claim 1 wherein there are
a plurality of radio receivers and a clock-driven differing pulse source for each of said radio
receivers.
4. The radio receiver operational checking system of Claim 3 wherein said
clock-driven differing pulse sources are spaced in time and waveform such that the audio
output of each radio receiver is audibly distinguishable from each other.
5. The radio receiver operational checking system of Claim 4 further
comprising light indicating means for each of said radio receivers to monitor visually said
audio short noise pulse outputs of said receivers and to turn on when said short noise
pulse output of said receivers coincide with said short pulses from said clock-driven pulse
sources being applied to said squelch control connection points of said radio receivers as
an indication of the operability of said receivers.

6. The radio receiver operational checking system of Claim 5 further
comprising audio signal responsive means for switching off said light indicating means for
each of said receivers when each of said receivers is receiving a radio signal.
7. Method for checking the operational status of at least one radio receiver
having a squelch circuit, comprising the steps of:
a) applying repetitive, short pulses to the squelch control connection
point of said radio receiver to deactivate said squelch circuit at regular intervals to provide
repetitive, short noise pulses in the audio output of said radio receiver, indicating that said
radio receiver is operational and awaiting a radio frequency signal,
b) said repetitive short pulses applied to said squelch control connection
point being of sufficiently short duration, so as to have a de minimus effect on the pilot or
radio operator.
8. The method of claim 7 wherein said repetitive short pulses being of
sufficiently short duration and small amplitude so as to be perceived almost subliminally
by the pilot or radio operator.
9. The method of Claim 7 further comprising the additional steps of applying
said repetitive, short pulses applied to the squelch control connection point of said radio
receiver to deactivate said squelch circuit at regular intervals are also applied to light
indicating means to indicate that said radio receiver is operational and awaiting a radio
frequency signal.
10. Method of checking the operational status of a plurality of radio receivers,each having a squelch circuit, comprising the steps of:
a) from separate, coordinated pulse sources, applying repetitive, short
pulses to the squelch control connection point of each of said radio receivers to deactivate
said squelch circuits at regular intervals, to provide repetitive, short, identifiable noise
pulses in the audio output of said radio receivers, indicating which of said radio receivers
are operational and awaiting a radio frequency signal,
b) spacing said repetitive short pulses, from each of said coordinated
pulse sources to each of said receivers, in time and waveform such that the audible
output of each of said radio receivers is audibly distinguishable from each other,

c) said repetitive short pulses applied to said squelch control connection
points being of sufficiently short duration, so as to have a de minimus effect on the pilot
or radio operator when present.
11. The method of Claim 10 further comprising the additional steps of applying
said repetitive, short pulses are also applied to light indicating means to indicate that said
radio receivers are operational and awaiting radio frequency signals, wherein said light
indicating means is normally switched off, but, in response to said repetitive, short pulses,
is switched on.
12. The method of Claim 11 further comprising the additional step of applying
an audio signal responsive means to switch off said light indicating means for each of said
receivers when either of said receivers is receiving a voice radio signal.

Description

CA 02036788 l998-ll-l0
RADIO RECEIVER OPER~TIONAL rUF~RTN~ METHOD AND SYSTEM
R~ ;~OuN~ OF THE lNvL..lION
FIELD OF THE lNv~:N~lON
This invention relates to a radio receiver operational checking
system using the radio receiver's active signal squelch circuit to
measure the operability of a radio receiver including identifying
which receiver is being checked where a plurality of radio receivers
are being monitored.
DESCRIPTION OF THE RELATED ART
For years, radio receivers used in aircraft, military, mobile
and other, critical radiant-energy communication links have used
circuitry known as "squelch" to make the receiver silent until a
"threshold" signal strength is reached, at which time full listening
power is activated. Receivers with squelch have a knob for the
operator to adjust to the critical silencing point, or "threshold."
In some receivers, the adjustment is preset and a pull-knob disables
squelch entirely, giving full background noise when volume is turned
up. Without the squelch circuitry, there is a continual noise in the
form of loud hissing or crackling, commonly known as background noise.
The noise is distracting and unpleasant; hence, the use of squelch
circuitry systems.
For example, in aviation, where almost everything is duplicated, it
is common practice to install two receivers, one for standby, even in
small aircraft. Although failure is unlikely, the chance exists that
any one of the thousands of electronic components in each of the
receivers may cause a system failure. If so, there is nothing to
indicate when a squelch-silenced receiver becomes a dead receiver.
This could be serious if the aircraft is being flown on instruments
in the clouds, if the controller must be heard in order to keep the
plane, pilot and passengers safe, or in any number of other situations
where it is crucial to have an operative radio.
Some pilots and communicators disable squelch and tolerate the noise
in order to know that the radio is live. Others leave the squelch
control on and trust blindly to fate. Still others bungle and foul
up their communication by inadvertently having the radio turned down
or off.
U.S. Patent No. 4,718,115 (Inoue), entitled "RADIO RECEIVER FOR
CARRYING OUT SELF DIAGNOSIS WITHOUT INTERFERENCE," is of interest as
a general reference in this case as it discloses the category of prior
art where a separate diagnostic signal is introduced in the path of
the incoming signal as it goes through

~ ~3lo73~
the radio receiver. This category of prior art is distinctively different from the present
invention in that the invention, which is to be described herein, periodically deactivates the
squelch circuitry as a method of determining the operational status of the radio and does
not use a separate diagnostic signal.
S SUMMARY OF THE INVENTION
In the following discussion, subliminal or near-subliminal refers to pulse duration
which is long enough to be heard without being intrusive or annoying.
This invention solves the problem of det~rmining the operational status of squelch-
silenced radios, and further adds the option of having an effectively silent radio when no
10 voice is present, by providing near-subliminal short bursts of full-sensitivity receiver noise
to indicate that the radio is operational and that the volume is adequately adjusted. In
addition, if more than one radio is being used, the system indicates which of the radios are
plopclly live.
Therefore this invention provides a monitoring means.for radio receivers which
15 employs squelch silencing, particularly the type used in aircraft communications, as well as
other types of communications.
This invention can also provide means to indicate which of several radios are active
and truly live, even though the receiver is essenti~lly silenced by squelch.
Also this invention can provide means for giving radio opel~lol~ assurance that
20 their receiving equipment has not failed and is live, even though the speaker or
headphones are essentially silenced by squelch.
This invention can also prevent inadvertent mix-ups of adjustment of multiple
communication radios or other colllll,ul~ication set-up on an aircraft.
In addition, this invention can provide means for informing a pilot or radio
25 operator coming new on the watch that there is reception and which particular radios are
adjusted live.
The foregoing advantages are achieved by the present invention by means of a
clock driven pulse source for each radio receiver to provide repetitive narrow pulses to

o 7~
deactivate momentarily each radio's noise squelch circuit at regular intervals, to give
indication that the said radio receiver is operational and awaiting a radio frequency signal.
Further advantages may be found in the following drawings and specification.
Specifically, the present invention provides a radio receiver operational checking
5 system comprising in combination:
a) a radio receiver including an active radio noise squelch circuit, set at a level
to elimin~te ambient atmospheric and receiver noise when no radio signal is being
received, and including a squelch control connection point where said squelch circuit can
be disabled by the application of a voltage of appropl;ate m~gnitllde~
b) a clock-driven pulse source for said radio ,eceivel providing repetitive short
pulses for application to said squelch control connection point to deactivate momentarily
said noise squelch circuit at regular intervals to provide repetitive, short noise pulses in the
audio output of said radio receiver indicating that said radio receiver is operational and
awaiting a radio frequency signal.
The invention also provides a method for checking the operational status of at least
one radio receiver having a squelch circuit, comprising the steps of:
a) applying lep~ ive, short pulses to the squelch control connection point of
said radio receiver to deactivate said squelch circuit at regular intervals to provide
repelili~e, short noise pulses in the audio output of said radio receiver, indicating that said~0 radio receiver is operational and awaiting a radio frequency signal,
b) said r~ ive short pulses applied to said squelch control connection point
being of sufficiently short duration, so as to have a de l~ nUS effect on the pilot or radio
operator.

CA 02036788 1998-11-10
BRIEF DESCRIPTION OF THE DRAWINGS
FIGURE 1 is a block diagram of the circuitry of the invention.
FIGURES 2A-L show the wave-form/pulse timing of the signals
generated using the invention.
DETAILED DESCRIPTION OF THE lNVL.~ lON
Referring primarily to FIGURE 1,the clock generator (Block 1) creates
a rectangular symmetrical wave-form of approximately two seconds
between transitions (FIG. 2A). Radio 1 pulse generator (Block 2) is
triggered when the transition goes from high to low, and generates a
ten millisecond pulse (FIG. 2B) which is sent to deactivate
momentarily the Radio 1 squelch circuit. Subsequent clock pulse
transition from low to high triggers the Radio 2 pulse generator
(Block 3). The output pulse pair (FIG. 2D) is likewise wired to the
squelch circuit of Radio 2 to deactivate momentarily the squelch and
pass the bursts of noise. These pulses are grouped to identify which
radio is being checked; thus, double pulse is Radio 2 and single pulse
is Radio 1.
The equipment as described above is adequate to perform the
audible communication checking claimed in this invention, since the
pilot or communicator can hear the periodic noise burst from the
"de-squelch" pulses. Note that the squelch system of the radio keeps
the radio silent when there is no signal.
This system may be enhanced with the use of indicator lights
(shown in FIGURE 1). Blocks 4, 5, 6, 7 provide visual indication to
show which radio or radios are live. A Light-Emitting Diode(LED)
connected to each radio shows when a particular radio is turned on and
adjusted for audible reception.
A noise burst amplifier (Block 4) "listens" on the headphone
audio line for any sound. This line would be squelched silent with
zero audio signal when no voice transmission was being received - if
it were not for the pulsed noise bursts. Block 4 amplifies these noise
bursts when heard at headphone level. The pulse, if present, is
amplified and shaped in Block 4 and is passed to a NAND gate (Block
5). This gate passes the pulse on to Block 6 (Radio 1 LED light pulse
stretch) if the noise burst pulse occurs coincident with Radio 1
pulses. Similarly, if headphone noise pulses are co-incident with
Radio 2 gating pulses, they are sent to Block 7 (LED pulse stretch for
Radio 2).
If Radio 1 and Radio 2 pulses are heard on headphones coincident
with their respective gating pulses, BOTH lights will come on. Blocks
6 and 7 (LED pulse stretch), when triggered from the gate, turn on the
LEDs for most of the four second period between

~3~7~
similar pulses. This gives nearly continuous light indication to show which radio is live.
The short period during which the indicator blinks dark in each period is a self-checking
feature which shows that the light is dependent on the audio noise pulse and is therefore a
valid indicator.
Blocks 8 and 9 disable both indicator lights when voice communication is being
received. This is shown in FIGS. 2K and 2L. Voice reception would confuse the
indication because voice audio signal is present at the sampling instants for the noise pulse
chec~ing This circuit solves the trouble of both lights coming on erratically when voice
is present by preventing either light from turning on when voice is present.
A logalilhlllic response is used to accommodate wide variations in audio level at
the headphone line.
In an embodiment of this invention, Blocks 1-3, 5 and 6 in FIGURE 1 are made up
of integrated circuit (IC) ships of the "TIMER" classification, which are standard eight (8)
pin chips. For compact p~c~ging, dual or multiple units can be used. The economical
type 555 or 556 have been used. Block 4 can be a 741 Op Amp IC and Block 5 a 7400
Quadrangle NAND Gate IC. Block 8 is an Op Amp IC such as a type 741; Block 9 is a
Timer IC such as a type 555. These parts are ill~l,dlive only and are not limiting in any
way.
The foregoing description has been directed to plefelled embo(liment~ of the
invention for the purposes of illustration and explanation. It will be apparent, however, to
those skilled in this art that many modifications and changes will be possible without
departure from the scope and spirit of the invention.

Representative Drawing