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For about the last 60 or 70 years, fire or alarm companies have utilized
straight line connections from a subscriber or customer to a central data
collection point as a basic means of implementing fire protection or an
alarm system. The ADT Company has engaged in these activities for a number
of years wherein a particular subscriber is wired to the central data
collection station of the company and the incoming data from several
customers is monitored by an individual at the station. He responds to
various lights, bells, or other signals to carry out the necessary
emergency actions which are dictated by the nature of the alarm. Quite
often, these central stations are connected to the various subscribers
through the use of dedicated lines. Dedicated lines are those which have
only one customer, or one class of customer, connected to them. Dedicated
lines are quite expensive and must be wired around the telephone terminal
equipment and must be handled in a unique manner as they cannot be
permitted to pass through the conventional cross-bar dialing equipment.
Even today, when electronic switching in terminals is contemplated, and
cross-bar equipment is obsolete, nevertheless, dedicated lines still
present problems to central telephone stations and equipment. Even if it
were possible to locate all dedicated lines in a conventional trunk line
extending from the central station to the outreaches of its given
neighborhood there are still problems in the use of dedicated lines.
Some have suggested the use of telemetry on various and sundry radio
frequencies such as those in an area where a television channel is not
used. Telemetry transmissions are, of course, not secure, and telemetry
transmitters and receivers require relatively expensive antennas. As the
frequency of the telemetry system increases, the cost of fabrication and
installation goes up. When the frequency becomes too high, one is forced
to resort to exotic antennas and wave guide systems for handling the
systems. It will be understood and appreciated that the cost and
complexity of such aa system is far beyond that which can be borne by
equipment of the nature described in the present disclosure.
Another problem with such systems is the possibility that the data
transmitted from the remote station will become garbled or lost. Where the
central station is receiving calls from several remote stations, one of
the bits of information transmitted is the identification of the remote
station calling. Also, a remote station may have several sensors connected
to it each of which indicates a different problem. For example, a remote
station may have one sensor to detect heat or smoke to indicate a fire,
another to detect intruders, and another to detect a malfunction in
equipment, such as a refrigeration system. If the data transmitted becomes
garbled, for example, if the signal received by the central station
indicates a fire when, in fact, there was an intruder or the refrigeration
system failed, the fire department would answer a false alarm. The
possibility of such malfunctions have greatly retarded acceptance of
automatic monitoring systems by fire and police departments and it is an
object of this invention to verify that the data transmitted by the remote
station is the data received by the central station.
Many other problems could be noted in passing. However, the foregoing
problems are representative of the cumulative problems presented with
equipment found competitive with the device of the present invention. The
device of the present invention constitutes an improvement of the
competitive equipment in numerous regards. The equipment of the present
invention will be described in detail hereinafter, however, a summary of
the equipment and its function will be given first.
A central station is adapted to be connected to a conventional pair of
telephone lines. While the equipment must be duplicated, the preferred
embodiment will be described with a single pair of lines. A number of
remote stations are located in the near vicinity. The stations are located
at a distance and spacing from the central station to permit dialing of
the central station with the conventional seven digit number. That is to
say, the remote stations are not located at such a distance where a long
distance call between the two stations would be required. The remote
stations are preferably placed about the premises or facilities of someone
desiring protection, and hence, the remote facilities are normally
connected with various alarm devices which respond to intruders, fire,
equipment failure, and the like. The remote stations are utilized as alarm
devices. Each remote station is equipped with an adjustable mechanism
whereby the telephone number of the central station is set into the remote
station. Once the main number is set in, the remote station is equipped to
call the central station. On the creation of the alarm condition as sensed
by various transducers connected with the remote station, it begins a
sequence wherein, in a predetermined sequence, the telephone number of the
central station is first called. When the call is completed, the central
station sends a verification signal to the remote station to indicate that
the call has been correctly placed. After this, data indicative of the
nature of the alarm and identification of the remote station is then
transferred to the central station. This is accomplished through
conventional telephone equipment which may include the exchanges of a
large, major city, or through equipment found in other locations.
The data is sent in spaced tone pulses. Upon the receipt of each data
pulse, the central station simultaneously sends a verification signal to
the remote station. If the proper verification signal is not received, the
remote station automatically breaks the connection and starts the cycle
over again, including dialing and data transmission. The dialing cycle is
repeated as well as the data transmission because the failure to receive
the verification pulse may be due to a break in the telephone connection.
Single repeating the data transmission obviously would be fruitless,
therefore, the dialing cycle is repeated each time a verification pulse is
not received for each data pulse transmitted.
In any case, the call is made and completed through conventional telephone
equipment and the equipment is then disconnected or permitted to continue
in the customary manner. The central station then has the data and such
alarm conditions can be implemented at that juncture as are necessary.
For a more complete understanding of the present invention, reference is
made to the following specification and drawings, which are:
FIGS. 1A, 1B, and 1C are schematic wiring diagrams of different portions of
the preferred embodiment of the remote station of the apparatus of this
invention; and
FIGS. 2A and 2B are schematic wiring diagrams of different portions of the
preferred embodiment of the central station of the present invention.
In the drawings, attention is first directed to the central unit or station
shown in FIGS. 2A and 2B. The central station will be described first, and
thereafter, the remote station shown in FIGS. 1A, 1B, and 1C, will be
described. It is believed that description of the central station, which
is relatively simple in comparison with the remote station, will slightly
enhance and make easier the understanding of the remote station. For this
purpose, attention is first directed to FIG. 2A of the drawings.
In FIG. 2A, the numerals 10 and 11 identify a pair of lines which are
adapted to be connected with a conventional telephone system. The lines
are customarily known in the trade as the tip and ring lines. They are
connected through various and sundry types of telephone equipment found in
a typical telephone system, the nature of which is beyond concern of the
present disclosure. The two lines are input with switching transistor 12
connected therebetween, which controllably meters circuit flow through the
primary of transformer 13.
In the initial or quiescent condition, lines 10 and 11 merely reflect an
open circuit back into the telephone equipment. This is what is
customarily required. An open circuit is one in which the line-to-line
impedence exceeds about 10,000 ohms, while a connection is normally
characterized by impedence in the range of 1,000 ohms. On receipt of an
incoming call, the signal is conducted down line 10 and through DC
blocking capacitor 14, rectifying diode 15, and to amplifier 16. Amplifier
16 turns on and forms an output signal on conductor 17. The signal on
conductor 17 is applied to tone generator 18 which forms a signal on
conductor 19 returning to NOR gate 20. The NOR gate 20 has second
conductor 21, and it will be presumed at this juncture that a signal is
present on conductor 21. When the two signals to the NOR gae coincide, it
turns on switching transistor 12 which thereby permits current flow in the
primary of transformer 13. Upon achieving current flow, the signals are
then coupled into the secondary of the transformer and into other
circuitry as will be described.
Returning to amplifier 16, it will be noted that it has conductor 23 which
is utilized to reset or terminate operation of the amplifier. Moreover,
conductor 23 is from a biquinary J-K count down circuit indicated by the
numeral 25. Pulses are supplied over conductor 17 to count down circuit 25
to be counted, and upon termaination of its necessary operation, it forms
a reset signal on conductor 23 which terminates operation of switching
transistor 12 and the functioning of NOR gate 20.
From the foregoing, it will be understood how pulses received by the
central station over the telephone lines from the remote station are
passed through transformer 13 and into the equipment which thereafter
responds to the pulses. At this juncture, the description will continue
setting forth the nature of the response to the pulses fed into the
equipment.
As shown in FIG. 2A, the secondary of transformer 13 is connected with
emitter follower transistor 26, which provides an input to additional
transistor 27. Transistor 27 is likewise an emitter follower and forms an
output signal connected to additional transistor 28. Transistor 28 is
connected to junction 29 where a signal in the form of one or two voltage
levels is formed. It must be emphasized that the equipment is operative
with pulses. Hence, frequency content is of no particular concern.
Inasmuch as it is dealing with pulses, the pulses are simply converted to
two levels at junction 29. The levels will be termed high and low, and
true and false for later discussion hereinafter.
Junction 29 then forms belevle signals which are input to additional NOR
gate 30. The output of NOR gate 30 is connected through storage capacitor
31, the value of which will be discussed hereinafter, and is then applied
to the input of additional NOR gate 32. As shown in FIG. 2A, NOR gate 32
is connected back to the input of gate 30. Through the use of appropriate
bias voltages connected through resistor 33, and the loading created by
resistor 34, circuit values can be readily calculated whereby a monostable
multivibrator is defined including NOR gates 30 and 32. In essence, the
circuit responds to the silence or absence of pulses which exists between
the spaced data pulses from the remote station.
The data transmitted to the central station is in the form of digits. There
must be a gap or space between adjacent digits. Adjacent digits must be
recognized and discriminated one from the other. The apparatus in question
thus forms a pulse on conductor 34 which is input to countdown circuit 25
to advance it from one state to the next. That is to say, countdown
circuit 25 counts the number of pulses in a first group or tone burst, and
thereafter counts another group. Two groups are separated as indicated by
the signal on conductor 34 which presets countdown circuit 25 to count
again from zero thereafter.
Conductor 37 identifies an end or word or end of group conductor which
comes up in level at the conclusion of the data transmitting sequence.
Conductor 37 is input to NOR gate 38 which forms an output through
switching transistor 39 to change the level on conductor 40. This
conductor is also connected with pushbutton switch 41 which is connected
to an appropriate positive voltage. Transistor 39 prepares conductor 40
for formation of a reset pulse. Moreover, a manual reset is provided
through implementation of switch 41. It should be noted that switch 41 is
unable to achieve a reset unless and until the complete counting cycle has
been completed. In other words, countdown circuit 25 must recognize and
count all pulses transmitted from the remote unit before a signal is
formed on conductor 37 thereby enabling operation of transistor 39. Switch
41 can be utilized to alter the level on conductor 40 to form a reset
pulse. The reset pulse is applied to countdown circuit 25 and also to
additional circuitry shown in FIG. 2B to reset the readout equipment as
will be described later in detail.
Countdown circuit 25 counts the number of groups or individual digits
transferred from the remote station and forms output levels on conductors
indicated by the numerals 42, 43, 44, and 45. The four conductors
mentioned are connected to four preferably similar blocks and provide
enabling signals directing the actual pulses themselves to individual
decoding circuits which will be described later. That is to say, counter
25 recognizes only a whole digit, not the value of the digit itself, and
forms enabling signals on the conductors 42, 43, 44, and 45. The apparatus
has been shown with four similar blocks although the number may be varied
in accordance with the needs of a particular installation.
The numeral 48 identifies a conductor which is connected to the secondary
of the transformer 13. Conductor 48 is likewise input to all the blocks,
A, B, C, and D. This is the input which provides the individual pulses to
all of the blocks. However, it will be recalled that only one of the
blocks is enabled. Since only one is enabled, the pulses input from
conductor 48 are passed only by one of the several devices indicated in
FIGS. 2A. The outputs are formed on a number of conductors which are
indicated by the numerals 49, 50, 51 and 52. These conductors are shown
continued on FIGS. 2B.
In FIG. 2B, conductors 49-52, inclusive, are shown input to additional
circuit elements which are preferably similar. The numeral 56 indicates
the first circuit element which is connected to the conductor 49. This
circuit element 56 is duplicated at additional locations in FIGS. 2B and
as shown, is provided with inputs from conductors 50, 51 and 52. Briefly,
a string of pulses is periodically gated through conductors 49-52,
inclusive. When the pulses are properly enabled by the equipment described
in FIG. 2A, pulses are then input through blocking diode 57 and series
dropping resistor 58 to transistor 59. Transistor 59 functions as a
conventional amplifying transistor having collector load resistor 60. Any
AC signals on the output of transistor 59 are grounded by grounded
capacitor 61. The output of transistor 59 is next input to NOR gate 62
which, in conjunction with additional NOR gate 63, forms a monostable
multivibrator. The monostable multivibrator further includes bias resistor
64, timing capacitor 65, and output series resistor 66. Dependent on the
component values selected for resistors 64 and 66 and the size of
capacitor 65, a pulse is formed by the monostable multivibrator which is
input to transistor 67. Transistor 67 provides an amplified output on
conductor 68 which is then input to decode driver 70. The decode driver is
particularly constructed and arranged for forming a visible output signal
on a seven segment indicator lamp, indicated by numeral 71. The decode
driver is a bought item, and it is believed and submitted that its details
of construction and circuitry are well known to those skilled in the art
and need not form a part of the present disclosure except to mention their
utilization. Moreover, decode driver 70 responds to the number of counts
which are input to it to appropriately luminate visible output tube 71 as
is the customary manner to form a signal which is readable visually by the
operator of the central station being described in FIGS. 2A and 2B.
As shown in FIG. 2B, the equipment within block 56 is duplicated on the
other three conductors. The seven segment decode driver is duplicated
also. The preferred embodiment of the remote station preferably provides a
data output which is four digits in length, and hence, four decode drivers
are utilized with four light output tubes.
It will be noted that conductor 40 from FIG. 2A is connected to each decode
driver. Conductor 40 is the reset which, on operation of manual switch 41,
terminates the signals indicated by the visible light output tubes and
resets the various decode drivers to zero.
While the foregoing sets forth the operation of the central station in
detail, it is helpful to point out two or three significant factors in its
operation. One is that it forms a tone which provides a verification
signal to the remote station upon receipt of each data pulse from the
remote station. Attention is redirected to tone generator 18 and NOR gate
20 which is driven by its output. In effect, the tone generator provides a
tone of sufficient amplitude and hence, sufficient excursion to drive the
NOR gate from cutoff to saturation rather rapidly. This creates a
relatively ragged square wave which is output through switching transistor
12 and hence forms a chopped signal in the primary of transformer 13. The
inductance of transformer 13 is sufficient to slightly round off the
square wave and to cause the transmission on the lines 10 and 11 of a
signal which is almost a clean signal. The signal transmitted has a
preselected frequency which is determined by that of the tone generator.
The signal is received by the remote station unit in the form of
verification of the receipt of a pulse from the remote station and the
length or duration of operation of the tone generator is coincident with
each pulse received by the central station from the remote station.
The foregoing describes the central station and its operation will now be
correlated to that of the remote station shown in FIGS. 1A, 1B, and 1C
together. While substantial quantities of telephone handling equipment
intervent between the two devices, nevertheless, attention is next
directed to the lines 10 and 11 which are shown in FIG. 1C of the
drawings.
A logical sequence of the operation of the remote station will next be
described. While the common point between the central and remote stations
is telephone lines 10 and 11 shown in FIG. 1C, nevertheless, it seems
appropriate to consider operation of the remote station shown in these
three drawings beginning with operation of a sensor, such as sensor 75
shown in FIG. 1B. The sensor is any type or sort of device which forms an
alarm condition by forming a voltage at an appropriate supply level on
conductor 76. Conductor 76 shown in FIG. 1B may be only a few inches long,
or may be of great length extending about the premises; and may be
connected to quite simple or complicated sensing devices. In any case
conductor 76 is an input from some form or fashion of switch means which
provides an increased voltage level on conductor 76. Conductor 76 may also
be paralleled to many alarm devices which function in different manners.
In any event, all the devices function to place an appropriate voltage
level on conductor 76 which is detected by the apparatus and which
initiates its operation.
Conductor 76 is input to a line finder delay circuit which is indicated
generally by the numeral 77. Circuit means 77 forms an output on conductor
78 after an appropriate delay. Given the chanced possibility that sensor
75 may close for an intermittent interval to possibly create a spurious
signal, line finder delay signal 77 preferably operates after sensor 75
has completed its connection for a substantial period of time, perhaps in
the range of five hundred milliseconds. While this factor can be adjusted
depending on the need and environment of the installation nevertheless,
after some delay, a signal is formed on conductor 78 indicating that line
finder delay circuit 77 is timed out. Similar to other delay circuits, the
line finder delay circuit is a pair of NOR gates appropriately connected
to form a single shot multivibrator. Conductor 78 is responsive to a
negative going signal from line finder delay circuit 77 to trigger
operation of additional circuitry.
Conductor 78 is input to NAND gate 79. Gate 79 is equipped with additional
input conductor 80 which comes from the power supply which is indicated by
the numeral 81 in the upper corner of FIG. 1B. Inasmuch as the negative
going signal on conductor 78 is present at the input, NAND gate 79 forms a
one output which is next input to NOR gate 82. The gate 82 is connected to
transistor 83 which is connected by means of an appropriate conductor to
the input of additional NOR gate 84. NOR gate 84, in cooperation with NOR
gate 85, and the appropriate resistors and capacitors, determine the
timing of the circuit and form an output on conductor 86 which is time
delayed. Conductor 86 is communicated through dropping resistor 87 to
transistor 88, which is utilized as a switch. Transistor 88 is connected
to variable voltage source 89 with grounding capacitor 90 for the purpose
of providing a bias level to clock 91. The bias level controls the clock's
speed. The clock is utilized for dialing, and hence, will form what will
be called dialing pulses hereinafter. The clock is also used during the
transmission of data pulses. The speed of the pulses is controlled by the
adjustment on resistor 89. For dialing, the pulses are adjusted dependent
on the particular make or manufacture of equipment utilized in the local
telephone exchanges. The nominal rate of dialing is ten pulses per second.
Further, the clock forms pulses which have the desired make-break ratio.
While clock 91 forms a rectangular wave form, it is not perfectly
symmetrical. The off and on time is varied, again dependent on the
particular make or brand of telephone exchange equipment. The clock
permits adjustment of this factor also, which is preferably tailored to
the equipment.
One output of the clock is on conductor 92 and another is through the
illustrated switching transistor and conductor 93. Conductor 93 is
communicated through switching transistor 94 and over conductor 95 which
extends from FIG. 1B to FIG. 1C. Conductor 95 is input through switching
transistor 96 and after clipping by diode 97, is input to phone lines 10
and 11.
As should be recognized, a certain interval is required before the
equipment seizes the telephone lines. An adjustment is provided to
accommodate this interval through the auspices of resistor 99 which is
then input to NOR gates 84 and 85 to provide the timed interval. The time
delay circuit which includes these two NOR gates thus permits an adequate
interval for seizure of the telephone lines by the equipment.
Continual control of transistor 96 is of some significance. Referring back
to FIG. 1B, numeral 100 indicates a NOR gate which has a pair of inputs
which are normally logic zero. With the logic zero inputs, the output
becomes a one which is passed by series resistor 101 and diode 102. This
causes transistor 94 to saturate which pulls line 95 close to ground
potential which cuts off transistor 96. Transistor 96 is the sole
connection between lines 10 and 11. In its normally conductive state, the
impedence between the lines 10 and 11 is approximately 900 to 1000 ohms.
When transistor 96 is cut off, the impedence between lines 10 and 11 rises
to approximately 10,000 ohms or greater. Hence, control of transistor 96
constitutes the source of the necessary impedence levels to reflect the
correct impedence into lines 10 and 11 as is required by the central
telephone exchange equipment.
Attention is next directed to gate 104 which is connected to line 78. When
line 78 changes levels toward a logical zero, this is sensed by NAND gate
104 and a one is formed on data line 105. The data line connects through
time delay circuit 106. An output is formed on conductor 107 which is
thereafter fed to circuitry shown in FIG. 1A which will be described
hereinafter. Briefly, time delay circuitry 105 suppresses noises found on
data line 105 and also shapes up the pulse for line 107 to be sure that
the circuitry which is connected to it and shown in FIG. 1A responds
properly.
Attention is next directed to FIG. 1A for explanation of the sequence
counter indicated by the numeral 110. It is believed unnecessary to detail
all operations of sequence counter 110 and so only a general or broad
discussion will be given. Conductor 107 provides the necessary counts to a
series of J-K flip-flops. The J-K flip-flops count through a cycle of ten
states. The three left-hand J-K flip-flops are connected differently than
the two right-hand flip-flops. A number of intermediate NOR gates serve as
the decode matrix for various and sundry values assumed by the J-K
flip-flops and their signals which uniquely enable ten NAND gates which
provide the sequence counter itself. Toggle circuit 111 forms the odd and
even numbers. The odd and even numbers are connected to several NAND gates
112 which form a ten state sequence counter. Obviously, the number of
states in the sequence counter can be varied dependent on the nature of
the telephone system, complexity of the message to be relayed, and so on.
In the preferred embodiment, the first NAND gate indicates the dwell time
which is associated with the seizure of the line and intiation of
operation of the automatic dialing equipment found in the remote station.
It has been assumed that the equipment is operated with a seven digit
telephone system. That is to say, local calls are indicated by seven
digits. The second through the eighth NAND gates in the grouping 112 are
associated with the seven digits of the local call. This then leaves the
eighth gate associated with the last digit of the call, and further
provides some dwell or interval to permit completion of the call and
answer by the central station which was shown in FIG. 2B. The ninth NAND
gate of gates 112 is utilized for data transmission itself, the nature of
which will be defined in greater detail hereinafter. The tenth and last
gate is associated with cutoff of the equipment.
Because of the need of flexibility of the equipment, preferably the seven
digits which are called by the equipment are adjustably set into the
equipment. Inasmuch as the equipment can be installed at many different
locations and the number to be called may vary from time to time or from
region to region, the flexibility is achieved through the use of a clock
dialing counter which is indicated by the numeral 115. This is shown at
the lower portion of FIG. 1A. The clock dialing counter is somewhat
similar to the counting mechanism 110 described. Inasmuch as it is quite
similar, it is believed unnecessary to give excessive details of the clock
dialing counter. Its use and function will be understood better through
the use of examples of its connection. Assume for sake of discussion that
the number to be called is 7777321. The seven output of clock dialing
counter 115 is thus connected to four consecutive NAND gates, the second
through the fifth gates inclusive, of the NAND gates 112. The three, two
and one outputs of the clock dialing counter are connected to the sixth,
seventh and eighth NAND gates 112, respectively. The flexibility of
connection permits the equipment to dial any combination of numbers as may
be desired. It is believed that the exemplary connection mentioned above
will provide an understanding of how clock dialing counter 115 is
connected with sequence counter 112 and the similarities of the two will
become readily apparent as an assistance in construction and manufacture
of the present invention.
The first eight NAND gates of sequence counter 112 are summed through a
pair of additional NAND gates as an expediency to avoid placing too many
inputs to a NAND gate. These NAND gates are then summed through an
additional NOR gate which is connected with conductor 122 which extends
from FIG. 1A to FIG. 1B to clock inhibit gate 123. As shown in FIG. 1B,
the connection of gate 123 is apparent from the drawings, but its
operation should be considered. When the seven digits representative of
the number to be called are transferred through NAND gates 112 and on the
conductor 122, gate 123 toggles to form an input for gate 82 previously
mentioned. Gate 82 in effect sums the signals from the gates 79 and 123
and functions through the fixed delay determined by NOR gates 84 and 85 to
initiate operation of clock 91. Thus, from gate 82 on, the circuitry
associated with clock 91 functions in the same manner as previously
described. When this circuitry functions in the customary and originally
described manner, clock 91 makes and breaks in the formation of a pulse
which is fed through conductor 93 to switching transistor 94 and conductor
95. Conductor 95 extends to FIG. 1C as previously mentioned and causes
transistor 96 to switch from off to on in simulation of dialing pulses.
Returning again to FIG. 1A, the eighth NAND gate of the gates 112 is
connected to conductor 116 which extends from FIG. 1A to FIG. 1B.
Conductor 116 is input to flip-flop 117. Its output is connected through
series resistor 118 and diode 119. When diode 119 becomes conductive, its
voltage level is sufficiently high to override any pulses from the clock
91. Thus, flip-flop 117 is utilized to disable clock 91 and to prevent its
further transfer of pulses to transistor 96 which simulates the dialing
pulse. Inasmuch as clock 91 finds multiple purposes, its pulses will be
utilized in other portions of the circuitry as will be described. After
dialing has been completed, it is undesirable that transistor 96 simulate
further pulses into the lines 10 and 11. For this purpose, flip-flop 117
and the cooperative circuitry mentioned prevents further transfer of clock
pulses to the dialing simulation circuitry, including transistor 92.
An additional output of flip-flop 117 is indicated at NAND gate 128. This
provides a signal on conductor 80 previously mentioned. Conductor 80
likewise causes disconnection of the line finder delay circuitry which
also is connected with the sensor itself. As will be recalled, time delay
circuitry 77 forms a delay to be sure that the equipment has seized the
telephone line. The similarity in the signals on conductors 78 and 80 will
be seen from this analogy.
Returning to the ninth gate of NAND gates 112 shown in FIGS. 1A, the number
130 indicates a gate which in effect sums the output of the ninth and
tenth gates and supplies it to NOR gate 131. NOR gate 131 forms an output
on conductor 132 which departs from FIG. 1A and is found in FIG. 1B.
Conductor 132 in FIG. 1B again connects with the clock inhibit gate 123.
Thus, this gate again functions to create pulses through operation of
clock 91. In summation, when the ninth gate is energized, clock 91 forms
pulses on conductor 92 but, keeping in view that clock 91 is a
multipurpose clock, no pulses are passed by transistor 94. This means that
clock 91 is utilized to generate data under controls which will be
described but there is no make and break in telephone lines 10 and 11
while this data is being transmitted.
Returning to FIG. 1A, as long as the equipment dwells on the ninth gate of
sequence counter 112, data is transferred through the ninth gate and into
the telephone lines in the following manner. The ninth gate is connected
by conductor 140 which extends from the ninth gate to the count to the
count storage register shown in FIG. 1C. In the upper portions of FIG. 1C,
conductor 140 is found. A storage register shown in FIG. 1C is generally
indicated by the numeral 142. It includes a right to left shift register
comprised of several stages of J-K flip-flops. The flip-flops, in
conjunction with NAND gates and appropriately wired presents form pulses
which are summed through NOR gate 143 which is connected to the conductor
140.
The broad function of storage means 142 should now be considered. Several
individual sensors are connected to it. The sensors are all indicated by
the numeral 148. The nature of the sensors is subject to variation and is
beyond the scope of the present disclosure. In any case, sensors 148 are
shown as a matter of convenience and not a limitation on the present
invention ranging in quantity up to nine. A particular sensor is triggered
and this is data that is useful and should be transferred through the
equipment. This data is variable data and is transferred through the
several conductors which are connected to the data storage means 142. The
data preferably includes five digits. The first is assigned to sensor 148
which is triggered and hence not preset. The next four digits indicate the
assigned call number of the particular remote unit. The ninth state of the
sequence counter transfers the variable data and is transferred in a
manner as will be described hereinafter. Of significance is the fact that
preset storage register means 142 shown in FIG. 1C forms a unique data
code adaptable for transmission which identifies the particular sensor and
the assigned call number of the remote station. All of this data is
transferred through the ninth gate previously mentioned.
It will be observed that preset storage register means 142 functions in
response to clock 91. It is connected with conductor 92 which inputs the
clock pulses. At the completion of counting, the output signal is formed
on the conductor 150 to so indicate.
The last state of sequence counter 110 should next be considered. The tenth
NAND gate indicates the end of data transmission and terminates operation
of the equipment. The tenth gate is connected through gate 130 to NOR gate
131 to form a signal on conductor 132. This is connected to clock inhibit
gate 123 shown in FIG. 1B. It inhibits operation of the clock and does not
toggle again, and hence, the clock is withheld indefinitely. However, the
state of the clock system described to this juncture resembles that of
earlier states, and hence, the equipment is still left in an "on"
condition. Attention is directed to conductor 152 which is connected to
the ninth gate and which provides the pulses from the ninth gate on
conductor 152 to the power supply shown in the upper left-hand corner of
FIG. 1B. There, conductor 152 is input to a switching transistor. The gate
switching transistor is indicated by the numeral 153. Switching transistor
153 controls operation of additional switching transistor 154. Transistor
154 is connected to conductor 155. Conductor 155 is next shown in FIG. 1C.
Conductor 155 provides power for an oscillator circuit which is indicated
generally by the numeral 160. The oscillator circuit forms a tone at a
pre-set frequency, such as 400 hertz.
At this juncture, strong emphasis should be placed on the two types of
pulses which are formed by the present invention. The dialing pulses are
formed by making and breaking lines 10 and 11. This is simulated by
transistor 96. Data pulses in the form of tone bursts are formed by
oscillator 160. Oscillator 160 forms a tone at the selected frequency
which is transferred through several stages of amplification through
coupling transformer 161. Transformer 161 is connected to line 10 and
inputs the tones into the telephone system. Thus, the two classes of
pulses have been described as make and break on the one hand, and tone
pulses on the other, and further, both are derived from the same clock 91.
The two types of pulses are both input to lines 10 and 11. The only
difference is the utilization of oscillator 160 to form tones and
switching transistor 96 to form the pulses.
Considering the sequence counter broadly, the transfer of dialing pulses
requires making and breaking of the line connection. On the other hand,
the transfer of data through the use of tone oscillator 60 requires that
the line be held. For this purpose, attention is directed to flip-flop 117
at the top of FIG. 1B. Conductor 175 extends from that flip-flop to FIG.
1C. In FIG. 1C, conductor 175 turns on switching transistor 176. When it
is turned on, it makes possible current flow through a complementary pair
of transistors 177 and 178. Diodes 179 and 180 merely steer current flow
to ground. With the complementary pair, it is of no consequence which line
of lines 10 and 11 is relatively positive. In essence, the primary of the
transformer 161 which is connected across lines 10 and 11 is connected in
series with a small resistance on the order of three to five ohms. In
effect, the line c | | |
