U.S. patent number 3,582,949 [Application Number 04/770,941] was granted by the patent office on 1971-06-01 for audiovisual annunciator with priority ranking for each condition.
This patent grant is currently assigned to Master Specialties Company. Invention is credited to Svenaage Forst.
United States Patent |
3,582,949 |
Forst |
June 1, 1971 |
**Please see images for:
( Certificate of Correction ) ** |
AUDIOVISUAL ANNUNCIATOR WITH PRIORITY RANKING FOR EACH
CONDITION
Abstract
An audiovisual annunciator for warning a system operator of the
occurrence of various monitored conditions within the system. A
signal generated in response to the occurrence of a monitored
condition energizes an associated warning lamp to visibly indicate
that the condition has occurred. An audio signal is simultaneously
generated and acoustically transmitted to the system operator. A
logic circuit assigns a priority ranking to each condition, such
that, when several conditions occur simultaneously, an audio signal
is generated for only the highest priority condition. If the
operator acknowledges the highest priority annunciated condition,
an audio signal is transmitted for the next highest priority
occurring condition. The operator may recall a silenced warning so
long as the condition continues to exist. A switch permits the
operator to test the warning lamps, the priority circuitry, and the
audio circuitry.
Inventors: |
Forst; Svenaage (Costa Mesa,
CA) |
Assignee: |
Master Specialties Company
(Costa Mesa, CA)
|
Family
ID: |
25090173 |
Appl.
No.: |
04/770,941 |
Filed: |
October 28, 1968 |
Current U.S.
Class: |
340/502; 340/514;
340/515; 340/519; 340/521; 340/692; 340/945; 360/12; 379/39 |
Current CPC
Class: |
H04M
11/045 (20130101); G05D 1/0055 (20130101); G08B
23/00 (20130101); G08B 25/012 (20130101) |
Current International
Class: |
G08B
23/00 (20060101); H04M 11/04 (20060101); G05D
1/00 (20060101); G08B 25/01 (20060101); G08b
019/00 (); G08b 029/00 (); H04q 003/00 () |
Field of
Search: |
;179/5,1.2MI
;340/414,221,27,412,214,183 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Urynowicz, Jr.; Stanley M.
Claims
I claim:
1. In a system having a plurality of condition sensing devices,
each of the devices being responsive to the occurrence of a
different condition to generate a signal an improved annunciator
for warning a system operator of the occurrence of a sensed
condition, said annunciator comprising, in combination:
a plurality of channels, each channel being connected to a
different condition sensing device and each channel being assigned
a priority ranking;
means in each channel for generating an inhibit signal in response
to a signal from the connected condition sensing device and in
response to an inhibit signal from the next higher priority
channel;
a plurality of audio signal-generating devices;
means responsive to an inhibit signal from the lowest priority
channel for simultaneously actuating said audio signal-generating
devices;
a plurality of normally off switching amplifiers, one connected to
each channel, each of said switching amplifiers having an input
connected to the output of one of said audio signal-generating
devices and each of said switching amplifiers having an output
connected to a common terminal;
means for turning on the switching amplifier connected to the
highest priority channel generating an inhibit signal;
means for audibly transmitting said common output of said switching
amplifiers to the system operator; and manually actuated means for
silencing the highest priority inhibit signal being generated and
for causing the switching amplifier connected to the next highest
priority inhibit signal being generated to turn on.
2. An improved annunciator for warning a system operator of the
occurrence of a sensed condition, as defined in claim 1, including
a memory means for each channel, means for setting each of said
memory means when the associated channel has been silenced, and
recall means for clearing said memory means, whereby, when said
memory means is cleared, the highest priority channel connected to
a device sensing a condition will again generate an inhibit
signal.
3. An improved annunciator for warning a system operator of the
occurrence of a sensed condition, as defined in claim 2, wherein
each of said memory means will remain set only as long as the
condition sensing device connected to the associated channel
continues to sense a condition.
4. An improved annunciator for warning a system operator of the
occurrence of a sensed condition, as defined in claim 3, including
means for testing said annunciator by simultaneously simulating all
conditions sensed by the condition sensing device.
5. An improved annunciator for warning a system operator of the
occurrence of a sensed condition, as defined in claim 3, including
a plurality of warning lamps, at least one of said warning lamps
being associated with each of said channels, and means for
energizing each of said warning lamps in response to a signal from
the condition sensing device connected to the associated channel
for each of said lamps.
6. In a system having a plurality of condition sensing devices,
each of the devices being responsive to the occurrence of a
different condition to generate a signal, an improved annunciator
for warning a system operator of the occurrence of a sensed
condition, said annunciator comprising, in combination:
means for assigning a priority ranking to each signal from the
condition sensing devices;
a plurality of endless recording tapes, each of said tapes being
associated with a different condition sensing device and each of
said tapes having a message recorded upon it;
means for simultaneously driving each of said tapes whenever at
least one of the sensed conditions occurs;
a plurality of transducers, at least one transducer being
associated with each of said tapes, each transducer having an
electrical output corresponding to the recorded message on the
associated tape whenever said tapes are driven;
a plurality of switching amplifiers, each of said switching
amplifiers having an input connected to the output of a different
transducer and each of said switching amplifiers having an output
connected to a common output terminal;
means for turning on the s witching amplifiers for the tape and
transducer associated with the highest priority condition sensing
device generating a signal;
means connected to said common output terminal of said switching
amplifiers for acoustically delivering to the system operator the
output of said switching amplifiers; and
acknowledging means for turning off said switching amplifiers for
the highest priority sensed condition and for simultaneously
turning on the switching amplifier associated with the next highest
priority sensed condition.
7. An improved annunciator for warning a system operator of the
occurrence of a sensed condition, as defined in claim 6, including
recall means for turning on the switching amplifier associated with
the highest priority acknowledged sensed condition and for
simultaneously turning off the switching amplifier associated with
the highest priority unacknowledged sensed condition.
8. An improved annunciator for warning a system operator of the
occurrence of a sensed condition, as defined in claim 7, including
means for simultaneously simulating the occurrence of all
conditions sensed by the sensing device to test the
annunciator.
9. An improved annunciator for warning a system operator of the
occurrence of a sensed condition, ad defined in claim 8, including
a plurality of warning lamps, at least one of said warning lamps
being associated with each of the condition sensing devices, and
means for energizing each of said warning lamps whenever the
associated device generates a signal.
10. An improved annunciator for warning a system operator of the
occurrence of a sensed condition, as defined in claim 9, including
a master caution lamp, and means for energizing said master caution
lamp whenever one of said switching amplifiers is on.
Description
BACKGROUND OF THE INVENTION
This invention relates generally to an improved warning system,
and, more particularly, to an annunciator for acoustically and
visibly warning an aircraft pilot of the occurrence of various
monitored conditions within the aircraft.
At the present time a number of different visual annunciators are
available for aircraft, aerospace, military, industrial, and
commercial applications. A typical visual annunciator includes a
caution panel having a large number of word-indicator lights. Each
light is connected to a sensing device which is responsive to the
occurrence of a particular condition within the monitored system
and each light has a legend indicative of the related condition.
When a monitored condition malfunction occurs, the associated
word-indicator light is energized to visibly announce the
occurrence of the condition.
When the annunciator is used in aircraft, there may be several
additions. A circuit is usually included to permit the pilot to dim
the indicator lights during night flying. Furthermore, since space
limitations usually require mounting the caution light panel at the
pilot's side, a single large red master caution light is located on
the aircraft control panel in front of the pilot to attract the
pilot's attention when a monitored condition occurs. When one or
more of the monitored conditions occur, the master caution light is
either turned or flashed. A switch on the caution light panel
permits the pilot to acknowledge the occurrence of a condition,
thereby extinguishing the master caution light. The master caution
light will remain extinguished until either a different one of the
monitored conditions occurs or the monitor is reset.
Attempts have been made to develop an annunciator for audibly
warning a system operator of a source of trouble in the system and,
possibly, for audibly stating corrective steps to be taken by the
system operator for eliminating the source of trouble. Audio
annunciators to date frequently have been unreliable and in many
instances lack priority circuits, and therefore are not suitable
for many uses, such as in aircraft. The prior art audio
annunciators typically lock onto the channel for the first
occurring condition, even though the condition is not as critical
as a subsequently occurring condition. In some cases, the audio
annunciator remains locked onto the channel for the first occurring
condition until reset by the operator, even after the condition has
been corrected. Another type of prior art audio annunciator has a
relay for each condition sensed. The highest priority sensed
condition blocks the relays for all lower priority conditions. As
long as a high priority condition exists, a lower priority
condition cannot be annunciated. There is no provision for the
operator to acknowledge an annunciated condition so that a
simultaneously occurring lower priority condition can be
annunciated.
With the increased use of aircraft, and especially helicopters, for
combat applications, the demand for a highly reliable, compact
audiovisual annunciator has been intensified. Under combat
conditions a helicopter pilot is called upon to operate guns as
well as to navigate and pilot the helicopter. Even if the pilot
notices that the master caution light has come on, he may not have
time to look at the caution panel to determine what condition has
occurred and to decide what corrective steps should be taken. An
audiovisual annunciator will solve this problem by audibly telling
the pilot that a condition has occurred and then telling him what
corrective steps should be taken.
SUMMARY OF THE INVENTION
The present invention comprises an improved audio annunciator
combined with a visual annunciator. The annunciator is connected to
a number of condition sensing devices in a monitored system to both
audibly and visually notify a system operator of the occurrence of
a monitored condition.
The annunciator has a plurality of channels, one connected to each
condition sensing device. Whenever a condition is sensed, the
associated channel switches on a caution lamp which s mounted on a
caution panel. The caution panel contains a caution lamp for each
channel, each lamp being of the word-indicator type bearing a
legend indicative of the condition sensed by the associated
device.
Each channel is assigned a priority ranking consistent with the
critical nature of the condition sensed by the connected condition
sensing device. Logic circuitry within each channel generates an
inhibit signal in response to either a signal from the associated
condition sensing device or an inhibit signal from the next higher
priority channel. Thus, when a condition is sensed by a device, the
associated channel produces an inhibit signal and, as a
consequence, all channels having lower priorities produce inhibit
signals. The inhibit signal from the lowest priority channel is
used to operate a master caution light, which is mounted in a
conspicuous location, and may additionally be used to operate a
flashing light on the caution panel.
A tape cartridge having an endless prerecorded tape and a pickup
head is associated with each channel. The tape cartridges are
simultaneously driven from a single motor driven capstan. The motor
is operated from a regulated power supply which is turned on in
response to an inhibit signal generated by the lowest priority
channel. The output of each pickup head is connected to the input
of a normally off switching amplifier. The switching amplifier
connected to the tape cartridge for the highest priority channel
producing an inhibit signal is turned on to pass and amplify the
signal from the connected pickup head. Since only one switching
amplifier is on at a time, the outputs of all switching amplifiers
can be connected to parallel and fed to the input of an audio
amplifier. The output of the audio amplifier may be connected to a
speaker system or to an existing communication system, such as the
pilot's intercom system when the annunciator is used in an
aircraft.
An acknowledging circuit is provided to allow the operator to
silence the audio portion of the annunciator. When the operator
momentarily pushes a silencing switch on a control panel, the
inhibit signal from the highest priority channel generating an
inhibit signal is silenced. As a result, the associated switching
amplifier is turned off and the switching amplifier for the next
highest priority channel generating an inhibit signal is turned on.
If none of the other channels is generating an inhibit signal, all
switching amplifiers and the power supply for the tape drive motor
are turned off since an inhibit signal will not appear at the
output of the lowest priority channel. Each channel includes a
memory which is set when the channel has been silenced and which
will remain set as long as a condition continues to be sensed by
the associated device. A recall circuit is provided to allow the
operator to recall the highest priority silenced inhibit signal by
clearing all set memories.
The control panel also contains an audio off switch which, when in
the off position, turns off the power supply for the tape drive
motor and blocks the acknowledging circuit. Thus, as long as the
audio is turned off, the operator cannot silence a channel and
therefore cannot turn the master caution lamp off. Still another
switch on the control panel permits the operator to selectively
test either the caution lamps or the audio and logic circuitry.
When the switch is in the "lamp test" position and the caution
lamps are working properly, all of the caution lamps on the caution
panel are turned on. When the switch is in the "audio test"
position, all of the sensed conditions are simulated. The audio
circuitry, logic circuitry and acknowledging circuitry for each
channel are then tested, sequentially according to the priority of
each channel, by successively operating the silence switch.
Accordingly, it is an object of this invention to provide an
improved audiovisual annunciator for warning a system operator of
the occurrence of monitored conditions within a system.
Another object of this invention is to provide an audio annunciator
giving instant transmission of a warning of higher priority than
the one that might be in progress.
Still another object of the invention is to provide an audio
annunciator in which the transmission of a warning may be silenced,
permitting a lower priority warning to be transmitted.
Another object of the invention is to provide an audio annunciator
in which a silenced warning, of higher priority than a warning in
progress, may be recalled as long as the condition associated with
the higher priority warning continues.
Still another object of the invention is to provide an improved
test circuit for an audiovisual annunciator.
Other objects and advantages of the invention will become apparent
in the following detailed description of a preferred form thereof,
reference being had to the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a block diagram of an audiovisual annunciator constructed
in accordance with the instant invention;
FIG. 2 is a schematic diagram showing the signal conditioning
circuitry, the control circuitry and the logic circuitry for one
channel, with the channel shown in a normal state;
FIG. 3 is a schematic diagram of the tape drive motor and capstan,
the tape cartridges and the audio-switching amplifiers;
FIG. 4 is a schematic diagram of the regulated power supply for the
tape drive motor and the master caution lamp driver;
FIG. 5 is a schematic diagram similar to FIG. 2, but showing the
channel in a condition sensing state;
FIG. 6 is a schematic diagram similar to FIG. 2, but showing the
channel in a condition sensing state as the silence switch is
operated;
FIG. 7 is a schematic diagram similar to FIG. 2, but showing the
channel in a silenced condition sensing state as the recall switch
is operated; and
FIG. 8 is a schematic diagram similar to FIG. 2, but showing the
channel in a normal state as the audio circuitry is tested.
DESCRIPTION OF THE PREFERRED EMBODIMENT
For convenience, the annunciator shown and described is a
20-channel audiovisual annunciator designed for use in an aircraft,
although the number of channels and the use are not intended to be
restricted to this. Referring now to FIG. 1, a flow diagram for an
audiovisual annunciator constructed in accordance with the instant
invention is shown. The heavy black lines connecting the various
blocks in FIG. 1 represent a separate connection for each of the
20channels while the lighter black lines represent either a single
connection or a number of connections for the different controls,
and the dashed line represents a mechanical linkage.
Each channel includes a signal conditioner 11, a logic circuit 12,
a lamp driver 13, one or more caution lamps 14, a tape cartridge 15
having an endless prerecorded magnetic tape and a pickup head, and
a switching amplifier 16. Each of the signal conditioners 11 is
connected to a different condition sensing device, which is built
into the aircraft or other monitored system. Each condition sensing
device generates a signal in response to a different sensed
condition, for example, a signal in response to a different sensed
condition, for example, a signal may be generated when the fuel is
low, when the landing gear is down, or when the oil pressure in an
engine is low. Since the various types of conditions sensing
devices may produce different types of signals, each channel has
signal conditioner 11 for converting the signal produced by the
connected device to a uniform logic signal, namely, to a logic one
or voltage for no signal and a logic zero or ground for a
signal.
Each of the 20 signal-conditioning circuits 11 is connected to a
logic circuit 12. Whenever an input to a logic circuit 12 is
grounded by the associated signal conditioner 11 in response to a
sensed condition, the logic circuit 12 switches on a lamp driver 13
to turn on a related caution lamp 14. The caution lamps 14 for all
channels are mounted in a group on a caution panel and are of the
word-indicator type, each lamp 14 having a legend indicative of the
sensed condition which causes the lamp to be turned on. A caution
lamp 14 will remain on as long as the related condition exists.
The 20 logic circuits 12 are assigned priorities according to the
critical nature of the various sensed conditions. Each of the logic
circuits 12 generates an inhibit signal in response to either a
signal from the connected signal conditioner 11 indicating that a
condition has been sensed or an inhibit signal from the next higher
priority channel. Thus, when a condition is sensed, the related
channel and all channels having lower priorities generate inhibit
signals. The logic output of the lowest priority channel is used to
turn on a master caution driver and lamp 17 and a power supply 18
for operating a tape drive motor 19, whenever an inhibit signal is
generated in the lowest priority channel. The tape drive motor 19
drives a single capstan 20 for simultaneously operating the 20 tape
cartridges 15. Each tape cartridge 15 includes a pickup head for
producing an audio signal when the tapes are driven. The 20 pickup
heads are connected to the inputs of the 20 normally off audio
switching amplifiers 16. Each logic circuit 12 is also connected to
an associated switching amplifier 16. The switching amplifier 16
connected to the highest priority logic circuit 12 which is
generating an inhibit signal is turned on to amplify and pass an
audio signal from the related tape cartridge 15. Since, at the
most, only one of the switching amplifiers 16 is on at one time,
the outputs of the 20 switching amplifiers 16 are connected in
parallel and fed to the input of a conventional audio amplifier and
transducer 21. In the case of an aircraft, the audio amplifier and
transducer 21 may be the pilot's intercom which is already built
into the aircraft.
A control panel 22 is connected to all of the logic circuits 12.
The control panel 22 includes a lamp and audio test switch, a
silence switch, a recall switch, an audio off switch, and a
conventional caution lamp dimmer switch. The operation of the
various controls will be described in greater detail later.
Referring now to FIG. 2, the various controls on the control panel
22 are shown along with the signal conditioner 11, the logic
circuit 12, the lamp driver 13, and the caution lamps 14 for the
highest priority channel. The circuitry relating to the highest
priority channel is shown enclosed within the dashed line 23, while
the various controls are shown above the enclosed dashed line 23
and a portion of the second highest priority channel is shown in
dashed lines to show the serial and parallel connections between
channels.
Each channel has a number of terminals 24 which are connected in
common to a conventional regulated power supply (not shown). When
commercially available logic elements are used, the power supply
may, for instance, have a regulated 5-volt output. The numerous
logic elements used in each channel are NAND gates. Each NAND gate
has a logic zero output, i.e., a grounded output, whenever all of
the gate inputs are a logic one, i.e., at the regulated voltage
supplied to the terminals 24. The NAND gates will have a logic one
output whenever at least one of the gate inputs is a logic
zero.
The different states of the logic circuits 12 are represented in
FIGS. 2 and 5--8, with the ground potential leads shown in heavy
black and the high potential leads shown in a lighter black.
The signal conditioner 11, which is shown at the left of the
channel, includes a resistor 27, a diode 28 and a capacitor 29. The
resistor 27, the diode 28 and the capacitor 29 are connected in
parallel between the power terminal 24 and a terminal 30. The
condition sensing device is shown as a normally open switch 31
which grounds the terminal 30 when a condition is sensed. With this
arrangement, the terminal 30 is normally at the voltage of the
power terminal 24 and is grounded when a condition is sensed. The
diode 28 and the capacitor 29 are included to reduce transients
when the switch 31 is opened and closed.
The terminal 30 is connected to one input of a NAND gate 32 while
the other input to the NAND gate 32 is connected to an audio test
line 33, which is normally at the potential of the power terminal
24. The NAND gate 32 will have a grounded output except when the
switch 31 is closed by a sensed condition or when the audio
circuitry is being tested. The output of the gate 32 is connected
in parallel to the inputs of two NAND gates 34 and 35. The two
gates 34 and 35 normally have high potential outputs since they
each normally have at least one grounded input. The normally high
output of the gate 35 is connected in parallel to the inputs of two
NAND gates 36 and 37. The power terminal 24 is connected to the
other inputs of the two gates 36 and 37 so that the outputs of the
two gates 36 and 37 are normally grounded. The normally grounded
output of the gate 36 and the power terminal 24 are connected to a
NAND gate 38, which has an output terminal 39. The output terminal
39 is normally at a high potential and is grounded when the switch
31 senses a condition. The output terminal 39 for each channel is
connected to an audio-switching amplifier 16, turning on the
switching amplifier 16 when the output 39 of the gate 38 is
grounded.
The normally grounded output of the gate 37 and the power terminal
24 are connected to the two inputs of a NAND gate 40. The output 41
of the gate 40 is connected in parallel to the inputs to two gates
37' and 38' located in the next lower priority channel. The two
gates 37' and 38' correspond to the two gates 37 and 38 in the
highest priority channel. The chief difference between the highest
priority channel and the lower priority channels is that the gates
37 and 38 in the highest priority channel each have an input
connected to the power terminal 24, while the gates 37' and 38' in
each lower priority channel have corresponding inputs connected to
the output 41 of the gate 40 in the adjacent, higher priority
channel. Therefore, the gate 37 in the highest priority channel
will have two positive inputs and a negative output whenever the
channel is in a normal state while the corresponding gate 37' in
each lower priority channel has two positive inputs and a negative
output only when the channel and all higher priority channels are
in normal states. The output 41' of the gate 40' for the lowest
priority channel is positive only when all channels are in normal
states. Similarly, the gate 38' in each lower priority channel will
have a positive input from the output 41 of the gate 40 in the next
higher priority channel whenever all higher priority channels are
in normal states and each gate 38' will normally have a negative
input from the associated gate 36'. If a gate 38' has a positive
input from the output 41 of the gate 40 in the next higher priority
channel and a positive input from the gate 36' because of a sensed
condition, then the output terminal 39' will be grounded to turn on
the associated audio-switching amplifier 16. However, if a higher
priority channel subsequently senses a condition, then the gate 38'
will have a high output 39' and the associated switching amplifier
16 will be biased off.
The NAND gate 34 has a normally grounded input from the gate 32 and
a normally high input from the audio test line 33. The output of
the gate 34, which is high except when a condition is sensed by the
switch 31 and the audio test line 33 is in the normally high state,
is connected to one input of a NAND gate 42. The NAND gate 42 has
two additional normally high inputs, one connected to the output
terminal 39 of the gate 38 and the other connected to a lamp test
line 43. The normally grounded output of the gate 42 is connected
to the lamp driver 13, which includes a resistor 44 and a
transistor 45. The resistor 44 is connected between the output of
the gage 42 and the base of the transistor 45. A high voltage power
source, for example, the 28-volt power source available in an
aircraft, is connected between a terminal 46 and ground. The
terminal 46 is connected through a current limiting resistor 47 and
one or more caution lamps 14 to the collector of the transistor 45,
while the emitter of the transistor 45 is grounded. As long as the
output of the gate 42 is grounded, the transistor 45 is biased off.
However, when one of the inputs to the gate 42 is grounded, the
output of the gate 42 will be at the voltage of the power terminal
24, switching on the transistor 45 to energize the caution lamps
14. Two caution lamps 14 are shown in parallel for safety purposes,
since incandescent lamps are inherently subject to failure, but the
statistical chance of both lamps failing at the same time is very
low.
The remaining portions of FIG. 2 will be described in detail in
describing the various modes of operation, as shown in FIGS.
5--8.
Referring now to FIGS. 2 and 3, the audio portion of the
annunciator is shown in detail. The single-elongated capstan 20 is
rotated by the tape drive motor 19 whenever power is applied to a
terminal 50 on the motor 19 by the power supply 18. 20 tape
cartridges 15, one for each channel, are mounted on a holder to
simultaneously engage the capstan 20. Each cartridge 15 includes a
prerecorded endless tape and a pickup head 51. Problems with pickup
head alignment are eliminated since the pickup heads 51 are
permanently mounted within the cartridges 15. The output of each
pickup head 51 is connected through a DC blocking capacitor 52 to
the base of a transistor 53. The proper bias is maintained on the
base of each transistor 53 by a voltage divider, including a
resistor 54 connected between the power terminal and the base of
the transistor 53 and a resistor 55 connected between the base of
the transistor 53 and ground. A resistor 56 is connected between
the power terminal 24 and an audio output terminal 57, which is
also connected in parallel to the collectors of the 20 transistors
53. The emitter of each transistor 53 is connected through a bypass
capacitor 58 to ground and through a resistor 59 to the output
terminal 39 of the NAND gate 38 for an associated channel. Since
the output terminals 39 are normally high, the transistors 53 are
all biased off. However, when one or more conditions are sensed,
the output terminal 39 for the highest priority condition sensing
channel is grounded. The grounded output terminal 39 turns on the
transistor 53 in the associated switching amplifier 16 to amplify
and pass an audio signal from the associated pickup head 51 to the
audio output terminal 57. Since at the most only one of the
switching amplifiers 16 is on at any given time, only one resistor
56 is needed between the power terminal 24 and the parallel
collectors of the transistors 53. As previously stated, the common
audio output 57 of the switching amplifiers 16 is connected to the
input of a conventional audio amplifier and transducer 21.
Referring now to FIG. 4, the master caution lamp driver 17 and the
regulated power supply 18 for the tape drive motor 19 are shown in
detail. Both the driver 17 and the power supply 18 are operated
from the terminal 46 of the available high voltage power source.
The driver 17 comprises a switching transistor 61 connected in
series between the power terminal 46 and an output terminal 62 and
related circuitry for controlling the conduction of the transistor
61. When the transistor 61 is conducting, current flows between the
collector, which is connected to the power terminal 46, and the
emitter, which is connected to the output terminal 62, to energize
a master caution lamp 63 and other optional devices such as a
flashing caution lamp (not shown) which may be located on the
control panel 22. The driver 17 has three inputs for switching on
the transistor 61 upon the occurrence of any of three conditions.
One input terminal 64 is connected either directly or through a
driver (not shown) to the output 41' of the NAND gate 38' in the
lowest priority channel. The additional driver stage may be
required to handle the current load. The input terminal 64, which
is normally high and is grounded when a condition is sensed in any
of the 20 channels, is connected through an isolation diode 65 to
the base of a transistor 66. The outer two input terminals 67 and
68 are also connected through isolation diodes 69 and 70,
respectively, to the base of the transistor 66. The terminal 67 is
connected to an audio off line 71 (FIG. 2) which is normally at the
voltage of the power terminal 24. When the audio circuitry is
turned off, the audio off line 71, and hence the input terminal 67,
is grounded. The other input terminal 68 is connected to a terminal
on a two-way test switch 72 (FIG. 2) which is grounded while the
audio circuitry is tested.
A resistor 73 connects the base of the transistor 66 to the power
terminal 46 and a second resistor 74 connects the base to ground.
The two resistor 73 and 74 form a voltage divider to bias the
transistor 66 in a normally conducting state. The emitter of the
transistor 66 is connected to ground through a diode 75, while the
collector is connected to the base of a transistor 76. The diode 75
biases the transistor 66 off when one of the input terminals 64, 67
and 68 is grounded, compensating for the voltage drop across the
diodes 65, 69 and 70. A bias resistor 77 is connected from the
power terminal 46 to the collector of the transistor 66. With this
arrangement, the transistor 66 is normally conducting. However,
when one or more of the input terminals 64, 67 and 68 are grounded,
the base of the transistor 66 will also be grounded, switching the
transistor 66 to a nonconducting state.
When the transistor 66 is nonconducting, the voltage on the base of
the transistor 76 will rise. The emitter voltage of the transistor
76 will rise as the base voltage increases, since the transistor 76
is connected in an emitter follower arrangement. The emitter of the
transistor 76 is connected to the base of the switching transistor
61 to control the conduction of the transistor 61. The transistor
61 will conduct when its base voltage is high and will be
nonconducting when its base voltage is low. A resistor 78 is
connected between the power terminal 46 and the collector of the
transistor 76 while a resistor 79 is connected between the output
terminal 62 and the common connection between the emitter of the
transistor 76 and the base of the transistor 61 to maintain a
proper bias on the transistors 76 and 61. A resistor 80 is
connected between the output terminal 62 and ground to bias the
transistor 61.
The regulated power supply 18 for the tape drive motor 19 is
similar to the driver 17, with the addition of a voltage reference.
A control transistor 83 is connected in series between the high
voltage power terminal 46 and the terminal 50 on the tape drive
motor 19 (see FIG. 3). The collector of the transistor 83 is
connected to the power terminal 46 while the emitter is connected
through an isolation diode 84 to the terminal 50 and the base is
connected to the emitter of a transistor 85 which serves as a DC
amplifier in a regulated current source. The power supply 18 has
two control inputs. In addition to being connected to the driver
17, the input terminal 64 is connected through an isolation diode
86 to the power supply 18. The terminal 64, which is normally at
the potential of the power terminal 24, supplies the base voltage
to a transistor 87 through a voltage divider comprising resistors
88 and 89. The emitter of the transistor 87 is connected through a
biasing diode 90 to ground and the collector is connected through a
resistor 91 to the power terminal 46. The collector of the
transistor 87 is connected to the base of the transistor 85. A
voltage reference comprising a Zener diode 92 in series with one or
more diodes 93 (the number of diodes 93 is selected to give the
desired reference voltage) is also connected from the base of the
transistor 85 to ground.
As long as the terminal 64 is at its normally high voltage, the
transistor 87 will conduct and a low voltage will appear on the
base of the transistor 85. When a condition is sensed in one or
more channels, the terminal 64 will be grounded, causing the
transistor 87 to become nonconducting, and the reference voltage
will be applied to the base of the transistor 85. A second input
terminal 94, connected between the isolation diode 86 and the
resistor 88, is connected to a normally open terminal on an
audio-off switch 95 (FIG. 2). When the switch 95 is in the
audio-off position, the power terminal 24 is connected to the
terminal 94 to maintain the transistor 87 in a conducting state,
regardless of the states of the logic channels.
As staged above, when the transistor 87 is turned off, the
reference voltage determined by the Zener diode 92 and the diode 93
is applied to the base of the transistor 85. A resistor 95 is
connected between the power terminal 46 and the collector of the
transistor 85 while the emitter of the transistor 85 is connected
to the base of the control transistor 83 and to the resistor 96,
which is connected to the emitter of the transistor 83. The
transistor 85 is connected in an emitter follower arrangement to
supply a constant current to the base of the control transistor 83,
regardless of fluctuations in the voltage at the power terminal 46.
A resistor 97 is connected between the emitter of the control
transistor 83 and ground, to bias the transistor 83. A diode 98 is
placed between the terminal 50 and ground to reduce any transients
which the tape drive motor 19 might produce.
Turning now to FIGS. 5--8, the operation of the logic circuits 12
and the controls is shown in detail. FIG. 5 shows the circuit of
FIG. 2, but with the highest priority channel sensing a condition.
The switch 31 is closed by the sensed condition to ground one of
the two high inputs to the NAND gate 32. When one input to the gate
32 is grounded, the gate 32 will have a high output, which will
cause both the gate 34 and the gate 35 to have grounded outputs.
The grounded output of gate 34 causes the NAND gate 42 to have a
high output, which biases the transistor 45 into a conducting
state. If the transistor 45 is conducting, the associated caution
lamps will be energized by a current flowing from the high voltage
power terminal 46, through the resistor 47, the parallel caution
lamps 14, the collector of the transistor 45, and from the emitter
of the transistor 45 to ground. The grounded output of the gate 35
will cause the gate 37 to have a high output. Since two high inputs
are now applied to the gate 40, the gate 40 will now have a
grounded output 41 which is connected to the gates 37' and 38' in
the next lower priority channel. The gate 37' will now have a high
output, regardless of whether a condition is sensed by the channel
in which the gate 37' is located. The gate 40' will now have to
high inputs and a grounded output 41' which is fed to the next
lower priority channel. Since the channels are serially connected,
the corresponding output 41' for each channel will be grounded. The
grounded output 41' for the lowest priority channel is connected to
the terminal 64 (FIG. 4) to turn on the master caution lamp driver
17 and the power supply 18 for operating the tape driver motor
19.
The grounded output of the NAND gate 35 in the highest priority
channel is also connected to the gate 36, switching the output of
the gate 36 to a high state. The gate 38 now has two high inputs
and a grounded output 39 which turns on the associated switching
amplifier 16 (FIG. 3). Since the grounded output 41 of the gate 40
is connected to the corresponding gate 38' in the next lower
priority channel, the output 39' of the gate 38' will be high,
regardless of whether a condition is sensed by the associated
channel. Since all corresponding outputs 39' for the lower priority
channels high, all of the corresponding switching amplifiers 16 for
the lower priority channels will be turned off.
The operation of the silencing circuitry is shown in FIG. 6. As in
the previous figures, heavy lines are used to represent grounded or
logic zero leads while light lines are used to represent high
voltage or logic one leads. Diagonal marks have been placed in FIG.
6 to indicate leads which change state when a silence switch 100 is
momentarily operated. The power terminal 24 is connected through a
pair of parallel resistors 101 and 102 to the "set" and "reset"
terminals of a flip-flop 103. When the silence switch 100 is in the
normal position, the reset terminal of the flip-flop 103 is
grounded and the set terminal is at the potential of the power
terminal 24. While the silence switch is momentarily operated, the
set terminal of the flip-flop 103 will be grounded and the reset
terminal will be at the high potential. The Q or normally high
output of the flip-flop 103 is connected through a bias resistor
104 to the base of a transistor 105. The power terminal 24 is
connected through a resistor 106 to the collector of the transistor
105 while the emitter of the transistor 105 is grounded. The
transistor 105 is normally conducting since its base is normally
high through the resistor 104. A silence line 107, connected to the
collector of the transistor 105, will be grounded or a logic zero
as long as the transistor 105 conducts. The silence line 107 is
connected in parallel to the inputs of NAND gates 108 in each logic
channel. Thus, when the silence switch is operated, the input to
the NAND gate 108 is momentarily high. The other input of the NAND
gate 108 is connected to the normally high output of a silence
flip-flop 109, and the output of the gate 108 is connected to the
clock input of the flip-flop 109. The flip-flop 109 also has an
input connected to the output terminal 39 of the gate 38. The
normally grounded output of the flip-flop 109 is connected to a
NAND gate 110. The other input of the NAND gate 110 is connected to
the normally high audio-off line 71, while the output of the gate
110 is connected to one input of the gate 35. The flip-flop 103 and
transistor 105 are used to control the potential on the silence
line 107 in place of a simple switch, since contact bounce in a
switch would cause several channels to be silenced.
In operation, when the silence switch 100 is momentarily operated,
the flip-flop 103 changes state, turning off the transistor 105.
The normally grounded silence line 107 will now appear at the
voltage of the terminal 24 and the gate 108 for each unsilenced
channel will have two high inputs and a grounded output. If the
input to the flip-flop 109 which is connected to the output
terminal 39 is grounded, the flip-flop 109 will change state. Since
only one channel, at the most, will have a grounded output terminal
39, only one of the flip-flops 109 will change state each time the
silence switch 100 is operated. If the audio-off switch 95 is
turned on, the gate 110 will have two high inputs and a low output
and the gate 35 will now have a low input and a high output. The
outputs of each of the gates 36, 37 and 38, and 40 will also
change. The output 39 of the gate 38 will now be high and the
associated switching amplifier 16 will be turned off. Since the
output 41 of the gate 40 is now high, the gates 37' and 38' in the
next lower priority channel will have high inputs and will be
responsive to a condition sensed by the associated channel. If none
of the lower priority channels are sensing conditions at the time a
condition sensing channel is silenced, the output 41' of the lowest
priority channel will become high and the master caution lamp
driver 17 and the power supply 18 will be turned off.
Once the flip-flop 109 in a condition sensing channel is set by the
momentary operation of the silence switch 100, it will remain set
until a recall switch 111 is operated or the switch 31 is opened by
the elimination of the sensed condition. When the switch 31 opens,
the output of the gate 32 is grounded, grounding a preset terminal
on the flip-flop 109 through a diode 112.
If the audio-off switch 95 is in the off position the silencing
circuit will not operate. When the audio-off switch 95 is in the
off position, the audio-off line 71 is grounded and each of the
gates 110 in each logic channel will have a grounded input. Since
the gate 110 has a grounded input from the audio-off switch 95, it
cannot change state while the silence switch 100 is momentarily
operated even though the flip-flop 109 changes state.
The operation of the recall switch 111 is shown in detail in FIG.
7. As in FIG. 6, diagonal marks are used to indicate leads which
change state when the switch 111 is operated. A recall line 113 is
connected from a normally open terminal on the switch 111 through
parallel isolation diodes 114 to the preset terminal of each of the
flip-flops 109. When the switch 111 is placed in the recall
position the preset terminal on each of the flip-flops 109 is
grounded and the Q output terminal of each flip-flop 109, which has
been previously set by the silence switch 100, is set high. As long
as the switch 31 continues to sense the occurrence of a condition,
the lines having the diagonal marks will change state when the
flip-flop 109 is cleared and the output 39 for the NAND gate 38 in
the highest priority condition sensing channel will again become
grounded, turning on the associated switching amplifier 16. If the
condition is eliminated before the recall switch 111 is operated,
the switch 31 will open and the gate 32 will have a grounded
output. The grounded output of the gate 32 will ground the preset
terminal of the flip-flop 109 through the isolation diode 112,
resetting the flip-flop 109 in a manner similar to which it is
reset by the recall switch 111.
The operation of the audio-test circuit is shown in detail in FIG.
8. When the test switch 72 is moved to the "audio test" position,
the normally high audio test line 33 is grounded. The gates 32 in
each channel will now have a high output, the same as if each
channel were sensing a condition. The logic circuit 12 for each
channel will now be in a condition sensing state and the highest
priority channel will have a grounded output at the terminal 39.
Thus, the switching amplifier 16 for the highest priority channel
will be turned on. Each channel is sequentially tested, according
to its priority ranking, by sequential operating the silence switch
100.
When the test switch 72 is moved to the "lamp test" position, the
lamp test line 43 is grounded. The lamp test line 43 is connected
to the NAND gate 42 in each logic circuit 12 to turn on each of the
lamp drivers 13. All of the caution lamps 14 should glow when the
test switch 72 is in the lamp test position, making it easy to
identify a burnt out caution lamp 14.
Although it has not been shown in the block diagram of FIG. 1, an
"end of message" signal may be recorded on each tape. An electronic
switch (not shown) responsive to the end of message signal may be
placed either in the audio switching amplifiers 16 or in the audio
amplifier and transducer 21 to block an audio output until the end
of message signal is reached. Thus, the audio signal will start at
the beginning of the recorded message on each tape cartridge
15.
It will be appreciated that other logic circuit arrangements may be
used, and that various modifications and changes may be made in the
remainder of the circuits without departing from the scope of the
appended claims.
* * * * *