Alarm data concentration and gathering system

A system is disclosed enabling bidirectional communications between a central station and a plurality of satellite stations over a switched data transmission network in which each satellite station initiates all communications between that satellite station and the central station such that priority data generated within a given satellite station is immediately transmitted to the central station, while routine data generated within each satellite station is stored for delayed transmission to the central station at different times previously set by the central station but monitored by local clocks within each of the satellite stations.

BACKGROUND OF THE INVENTION 
1. Technical Field 
This invention relates to communications systems, in particular to those 
enabling automatic communications between a central station and a 
plurality of satellite stations. 
2. Background Art 
Data communications systems enabling connections to be automatically 
established, such as through commercial telephone systems, between a 
central data processing station and a plurality of satellite stations are 
well known. Such systems are totally oriented to central station control, 
wherein the central station controls the time at which a given satellite 
station communicates with the central station, controls the initiation and 
termination of all such communications, and controls the nature of such 
communications once established. 
For example, U.S. Pat. No. 3,245,043 (Gaffney and Kusnick) is directed to a 
message communication system in which a plurality of widely spaced apart 
satellite stations are connected to a central data processing unit. In 
such a system, each satellite station includes means for storing 
information which is subsequently transmitted to the central station for 
processing. In that system, all satellite stations are serially connected, 
such that data from the most remote station flows through all closer 
satellite stations prior to being received by the central station. Each 
station is provided with a gate which senses the absence of signals from 
other satellite stations directed toward the central station, and 
thereupon pre-empts the transmission line in order to transmit signals 
stored within its own information store. 
In U.S. Pat. No. 3,629,831 (Mikus and Harvey), an apparatus for controlling 
data transmissions between a central station and a plurality of satellite 
stations in which a data conversion unit is provided within the central 
station to enable data to be transmitted to and received from the 
satellite stations in serially encoded digital form, whereas it is 
communicated to a central data processor in parallel encoded digital form. 
In this system, a satellite station may request communication with the 
central station, whereupon a selecting means within the central station 
randomly detects that a given station is in condition to transmit data and 
thereupon controls the transmission and receipt of information transmitted 
from that satellite. In both of the systems noted above, a given satellite 
that is already connected to the central station precludes connection of 
other satellite stations to the central station such that all 
communications from other satellites, both of routine and priority type 
information, would be thwarted. 
Other communications systems are also known which operate on a pure 
interrupt basis, that is, the occurrance of an alarm signal from a sensor 
associated with a satellite station immediately causes that satellite to 
activate automatic dialing equipment, thus securing an available 
transmission line for immediate transmission of that alarm signal to a 
central station. 
DISCLOSURE OF INVENTION 
In contrast to such data communication systems as discussed above, the 
system of the present invention includes features whereby desirable 
aspects of systems in which satellite stations are individually polled for 
subsequent bidirectional communications with the central station are 
provided together with certain aspects of systems wherein satellite 
stations are enabled to communicate with the central station solely on a 
priority interrupt. The present system thus includes a plurality of 
satellite stations and a central station, bidirectional communications 
between which are enabled via a switched data transmission network such as 
a conventional telephone network, and enables routine data to be received 
and held within each of the satellite stations, and to be subsequently 
transmitted to the central station at different predetermined times upon 
the initiation of communications therewith under local control of each 
satellite station. 
The central station of the present system thus includes a master clock 
which controls the timing of the overall system, and which maintains 
ongoing time settings, while each satellite station includes a local clock 
which is responsive to instructions from the master clock and which 
controls the initiation of routine communications from that satellite 
station to the central station at predetermined times. 
Further, the central station includes a memory bank within which data 
signals associated with each satellite station are stored at locations 
having designated addresses associated therewith. The central station also 
includes means for receiving data signals from the satellite stations and 
for transmitting data signals to the satellite stations. 
To enable the central station to process data signals received from a given 
satellite station at predetermined times under direct control of the local 
clock within each satellite station, the central station also includes 
means for initiating access to a given address within the memory bank in 
response to receipt of a communication originating within a given 
satellite station, together with means for routing the data signals 
received as a part of the originating communication to the designated 
address within the memory bank which is associated with that satellite 
station. 
Each satellite station is kept current as to the on-going time and the time 
for the next required communications by further providing the central 
station with means for accessing the master clock to provide instructions 
indicative of the real-time setting of the master clock and of the time 
setting for the next required satellite communication, which time setting 
is different for each satellite station and with means for coupling those 
instructions to the transmitting means for transmission to the satellite 
station then in communication with the central station. The central 
station is also provided with means for terminating a given communication. 
As noted above, each satellite station includes a local clock which is 
responsive to the instructions from the master clock and which thus 
controls the initiation of communications and the transmission of routine 
data signals to the central station at the predetermined time for that 
satellite station. Each satellite station also includes means for 
synchronizing and adjusting its local clock in response to instructions 
from the master clock, store and forward means for accumulating routine 
data for transmission to the central station at the predetermined time for 
that station, means responsive to its local clock for initiating 
communications with the central station, and means for inputting routine 
data into the store and forward means. 
In a preferred embodiment, each of the satellite stations further includes 
means for inputting non-routine data into the store and forward means and 
means for initiating said communications with the central station at any 
time on a priority interrupt basis for enabling immediate transmission of 
the non-routine data.

DETAILED DESCRIPTION 
Referring now to FIG. 1, it may be seen that the system of the present 
invention includes a central station 10 and a plurality of satellite 
stations 12, 14, 16, and 18. As is there shown, each of the satellite 
stations is coupled to the central station 10 via a data transmission 
network, which network is preferably a conventional automatically dialed 
telephone system. As such systems are conventional and do not encompass 
the present invention directly, no further details thereof are provided 
herein. Each of the satellite stations 12 through 18 is further provided 
with a plurality of sensors, those associated with satellites 12 through 
16 being identified as components 20, 22 and 24, respectively. Sensors 26, 
28, 30, 32 and 34 are associated with satellite station 18, which is shown 
in expanded form in FIG. 1, and are further identified as sensors 1 
through N, thus indicating that any given satellite may be served by as 
many sensors as is desired for a given application. The typical sensors 
utilized with the satellite stations of the present invention will thus 
preferably include perimeter, window and door switches suitably installed 
so as to indicate the condition of a given entry way, intrusion detectors, 
fire and smoke alarms, and the like. 
The basic construction of the central station 10 is further shown in FIG. 1 
to include a host Central Processing Unit (CPU) 36, a master clock unit 
38, a central memory 40, a transmitter unit 42, and a receiver unit 44. 
The Central Processing Unit 36 thus functions as an overall controller in 
that it processes information received via receiver 44 and routes 
information therefrom to the memory 40, from whence it may be outputted on 
lead 46 to suitable display devices (not shown). Similarly the host CPU 36 
controls the master clock 38 such as to implement outputting of 
appropriate signals from the transmitter 42 to a given satellite station 
via the transmission network. 
In like fashion, each of the satellites A through N, such as shown in 
enlarged form for satellite N, shown as component 18, comprises the 
components shown in the block diagram of FIG. 1. Thus each satellite 
station may be seen to include an input data control processor 48, a 
buffer memory 50, a local clock 52, a logic processor unit 54, a data 
store-and-forward unit 56, a receiver 58, and a transmitter 60. As is 
schematically shown in FIG. 1, the input data control processor 48 thus 
functions to receive input signals from all of the respective sensors 
coupled to a given satellite station and to output signals having a common 
format representing the signals from the respective sensors to the logic 
processor unit 54. The processor unit 54 functions much as the host CPU 36 
in the central station in that it further controls the processing of the 
signals within the satellite station, either routing signals from the 
control processor 48 into the data store-and-forward unit 56 for temporary 
storage, or for controlling the subsequent transmission of such stored 
information via the transmitter 60 through the data transmission network, 
and thence to the central station 10. The logic processor 54 also controls 
the flow of signals to and from the local clock 52 to thereby synchronize 
the various signal processing operations within the satellite station, as 
well as to enable updating and resynchronization of the local clock with 
the master clock 38 within the central station, as instructed by signals 
received from the central station 10 via the receiver 58. 
While the respective components of the central station 10 and each of the 
satellite stations 12 through 18 are thus shown in the block diagram of 
FIG. 1, the functions performed by each of the respective stations is 
preferably described via the combined flow diagram shown in FIGS. 2a 
through 2e. In the present system, while control over the operations 
within each of the satellite stations A-N is under the control of the 
central station 10, and more particularly, under the control of the host 
CPU 36 within the central station, each of the satellite stations is 
provided with the capability of independently controlling its own 
operation. Each satellite station thus has the sole capability of 
initiating communications with the central station, albeit at 
predetermined times earlier dictated by the central station. This feature 
is immediately apparent in FIG. 2a, where it is indicated that the 
beginning, or "start", 62 of all communications is initiated within the 
satellite station. At periodic, and closely spaced intervals, as 
controlled by the local clock 52, the state or condition of each of the 
sensors coupled to the given satellite is examined as shown in block 64. 
If such an examination indicates that the given sensor is in a state 
indicative of the absence of the occurrence of an event, such as a window 
or door switch being in an open condition, or the like, a "commutate 
sensors" signal is provided (block 66) on lead 68, which then causes the 
subsequent examination of a second sensor. On the other hand, if the 
examination indicates that an event has occurred, the time at which the 
occurrence of the event has been registered is determined by reading the 
local clock as shown in block 70 and information representative of the 
identity of the event and the time of occurrence thereof is stored in the 
buffer memory 50, as shown in block 72. Concurrently, the nature of the 
event is compared against information previously stored in the control 
processor 48 as shown in block 71. If it is thus determined as shown in 
block 74, that the event is routine, a commutate sensors signal is 
similarly provided on lead 68 as noted hereinabove, such that the state of 
a subsequent sensor is next interrogated. On the other hand, if it is 
determined that the occurrence is not routine, thus indicative of an 
emergency or a priority message, the non-routine emergency signal is 
provided on lead 76a. Basically, once information representative of an 
event and time of occurrence thereof has been stored in the buffer 50, the 
information remains therein until instructions are received to read the 
information from the buffer as shown in block 78. However, due to finite 
capacities of buffer memories, in a preferred embodiment, periodic 
inspection of the contents of the buffer memory 50 is desirable. Thus, if 
the inspection indicates that the buffer is not filled to capacity, as 
shown in block 82, further inputting of information into the buffer is 
enabled. Alternatively, if the inspection indicates that the buffer is 
full to capacity, an additional output signal on lead 76b is provided. 
The manner by which each satellite station controls the initiation of 
routine communications to the central station is further evident from the 
instruction blocks 77, 84 and 86, which indicate that the local clock 52 
is periodically read (block 84) and compared against a pre-established 
time setting held in memory (block 79) to determine whether the time 
previously set within the memory (block 79) upon instructions from the 
central station has transpired. If it is not yet time to report, a signal 
is provided on lead 88 that causes the local satellite clock 52 to be read 
again on the next periodic cycle. Alternatively, if it is then determined 
that it is time for the satellite station to report to the central 
station, a further output signal is provided on lead 76c. 
As noted above, it may thus be seen that a transmission initiate signal 
will be provided on lead 76 under at least the three sets of conditions 
previously discussed, namely that a non-routine event has occurred (76a), 
that the buffer memory 50 is full (76b), or that the time for a periodic 
report has occurred (76c). Further, as noted hereinbelow, in the event 
that data transmitted to the central station has been found not to be 
properly received at the central station, a further transmission initiate 
signal will be provided on leads 76d and 76e. The occurrence of such an 
initiate signal on lead 76 thus initiates the dial sequence shown in block 
90. This causes an automatic dialing apparatus, which as noted 
hereinabove, is not an integral part of the present invention, to activate 
a dialing signal which is transmitted through the transmission network as 
indicated in FIG. 1, which dialing signal is thereupon detected within the 
central station as shown in operation block 92. 
When the dialing signal is thus detected, a pickup instruction is initiated 
as shown in block 94, and an acknowledgment of the appropriate receipt of 
the ringing signal is transmitted as shown in block 96 on lead 98. Upon 
receipt of the acknowledgment signal as indicated in block 100, assuming 
that acknowledgment is indicated, the satellite station then proceeds to 
transmit to the central station its own address as shown in block 102 on 
lead 104, thereby identifying itself, and upon completion of the 
transmission of the address, reads the buffer as shown in block 78 and 
transmits stored information on lead 104 as instructed by block 105. 
Conversely, if the acknowledgment is not indicated within a predetermined 
time "T-1" as monitored by block 108, the satellite station "hangs up" as 
indicated in block 110, and reinitiates the dialing sequence as indicated 
on lead 76d and block 90. 
At the same time that the acknowledgment signal is transmitted to the 
satellite station on lead 98, in a preferred embodiment, a timer within 
the central station 10 and having a preset running duration, for example 
10 seconds, is activated (112). Upon expiration of that time period, as 
shown in 114, the central station automatically and unequivocably "hangs 
up" as indicated in block 116. Alternatively, if the timed period has not 
lapsed, the processing continues, as indicated in block 118, and data 
stored within the buffer 50 of the satellite station is then transmitted 
on lead 120 to the central station. This optional feature thus acts as an 
ultimate fail-safe provision. Should all other message terminating 
provisions of the system fail, it ensures that the central station will 
"hang-up", thereby severing the communications link and freeing the line 
to receive other transmissions after a time long in excess of that 
required to transmit even the longest routine or priority message. 
Upon receipt of stored data in the buffer as indicated within block 122, 
the central station processing unit 36 first receives the address of the 
satellite transmitting the data as indicated in block 124, which 
information is transmitted on lead 126 and stored within the memory unit 
40 of the central station (block 127). The central station next receives 
the actual transmitted data as indicated in block 128 and upon 
confirmation that all of the data has been properly received, as indicated 
in block 130, transmits that data to the central station memory 40 as 
indicated in block 132 where it is stored (bolck 133). In the event that 
the data is not appropriately received, a data not-acknowledged signal is 
transmitted, as indicated at block 134, via line 139 to the satellite 
station. Alternatively, if the data is appropriately received and sent to 
the memory as indicated in block 132, a data acknowledged signal is 
transmitted on line 139 as indicated at block 136. If the data 
acknowledged signal is received by the satellite station, it goes into a 
"wait" mode, as indicated by blocks 138 and 140. Alternatively, if the 
data not-acknowledged signal is received, a repeat signal is provided on 
lead 141 which initiates a retransmission of the satellite's address, as 
indicated in block 102, and of the data stored in the buffer, as indicated 
in block 105 on lead 120. 
Upon storage (block 133) of the data within the memory 40, the memory 40 is 
read (block 143) and confirmation of proper receipt and storage of the 
data within the memory 40 is then indicated by block 142. In the event 
that check indicates that the data was not properly recorded, a signal is 
provided to cause the data to be retransmitted to the memory as indicated 
in block 132. Alternatively, if the memory properly received and stored 
the data, the master clock 38 is then interrogated to obtain a signal 
representing the ongoing time and the time at which the satellite station, 
then in communications with the central station, is required to next 
report, as indicated in block 144. This information is then transmitted to 
the satellite station as indicated in block 146. Within the satellite 
station, the confirmation of the appropriate receipt of the time 
information is then determined, as indicated in block 148. In the event 
the time data was incorrectly received, a time data not-acknowledged 
signal is sent, as indicated in block 150, while if the data is properly 
received, a data-acknowledged signal is transmitted, as indicated in block 
152. Upon receipt of one or the other signals within the central station, 
as indicated in block 154, if the data was improperly received, a signal 
is provided on lead 156, causing the time data to be retransmitted, as 
indicated in block 146. Alternatively, if the time data was appropriately 
received, the central station then "hangs-up" as indicated in block 158, 
thus terminating the entire message sequence. 
Similarly if the time data was properly received within the satellite 
station, the satellite station also "hangs up" as shown in block 160. On 
the other hand, if the time data was not appropriately received, a data 
not-acknowledged signal is sent as indicated in block 150, and if no 
signal is received in the satellite station prior to expiration of time 
T-2, as indicated by block 162, the satellite station is made to "hang-up" 
unconditionally (via line 161). This precaution prevents unauthorized 
equipment from keeping the satellite station "off-hook" for a protracted 
period of time. This same signal issued by block 162 causing the 
unconditional "hang-up" also reinitiates the dialing sequence via lead 
76e. If, as determined in block 148, the master clock time and the next 
scheduled report time are correctly received, not only is the satellite 
station caused to "hang-up" as mentioned previously, but a signal is 
provided which resets the satellite station local clock (block 64) and 
stores the newly scheduled next report time. These events terminate the 
transmission from the satellite station. 
Once the system described in FIGS. 2a through 2e is understood, it can 
easily be seen that a much simplified embodiment could be used in such 
applications as reading utility meters and reporting said readings to a 
central station periodically. In such an embodiment, it is only necessary 
for the local clock to be compared against the next scheduled report time. 
There are no unscheduled events. When the time has come for the satellite 
to report, it simply reads the value indicated by the meter, stores it, 
and initiates communication with the central station. All the error 
checking protocols would continue to be observed and the local satellite 
clock and next scheduled report time would again be synchronized to that 
of the host CPU. 
It may thus be seen that the flow of these respective signals as indicated 
in the flow diagram described above in conjunction with FIGS. 2a through 
2e, enables each of the satellite stations to communicate on a 
quasi-independent basis with the central station, such that all 
communications between any given satellite station and the central station 
are initiated by that satellite station, priority data from such satellite 
stations being transmitted to the central station without delay while 
routine data is transmitted from the satellite station at the prescribed 
times as instructed by the central station. 
FIGS. 3a through 3d set forth in more detailed form a preferred flow 
diagram indicating the manner within which signals are preferably 
processed within the central station 10 of FIG. 1. Accordingly, in FIG. 3a 
it may be seen that the central station will pick up the line as indicated 
in block 94 either upon the detection of a ringing voltage, block 92, 
(both of which blocks are also indicated in FIG. 2b) and also upon receipt 
of a command from the central station operator as indicated in block 170, 
or upon indication of an automatic busy signal as indicated in block 172. 
The signal produced by a central station operator as indicated in block 
170 thus enables testing of line conditions by a central operator to 
insure the operability of the incoming line from the satellite stations 
and to insure that the system is in appropriate condition to receive 
communications initiated by any one of the satellite stations. The 
"automatic busy" signal indicated in block 172 is generated as a result of 
several diagnostic self tests which include interrogation for proper power 
supply voltages, proper operating conditions of the phone line, whether 
the printed circuit cards are plugged into their addressed slots, etc. In 
a preferred embodiment, upon detection of a defective condition thereof, 
the central station "picks up" the line, for example, causing a 
WATS-rotored network to switch to a next higher incoming line, thereby 
ensuring that the central station is always in condition to receive a 
communication initiated from any one of the satellite stations. 
A signal from any of the sources 92, 170 or 172 is thus coupled through OR 
logic 174 to the pick-up line 94, causing the immediate transmission of 
the higher of two frequency carrier tones (such as a 2 kilohertz tone) to 
the satellite station, as indicated in block 176. Simultaneously, the 
timer operations 111, indicated as optional in FIG. 2c, are initiated. As 
shown in more detail in FIG. 3a, these operations include a 10 second 
clock 178, a 1 second clock 180, and a 3 second clock 182. Upon 
transmission of the high carrier signal, the 10 second clock begins its 
countdown as shown in block 178. In contrast to the 10 second period thus 
initiated, typical data transmissions take between 2 to 4 seconds, there 
being required approximately a 2-second initial delay period to allow the 
transmission lines to settle into a quiescent state, and between 2 
milliseconds to 2 seconds of actual data transmission time. Accordingly, 
as indicated in block 184, upon expiration of the 10 second clock period 
as indicated on lead 186, the system hangs up as instructed in block 188. 
Alternatively, if the 10 second clock period has not expired, a signal is 
provided on lead 185, causing the processing of the incoming signals to 
proceed. 
The running of the 1 second clock as indicated in block 180 insures that 
the satellite station has received the central station carrier tone and 
has in turn transmitted its own carrier, such as a 1600 hertz signal, 
which signal has been received by the central station prior to the 
expiration of the 1 second clock, as indicated in block 190. If the 
completion of that exchange of carrier signals has not occurred, as 
indicated at line 192, the system further hangs up as indicated in block 
188. Contrariwise, if the carriers have appropriately been received, 
further processing of signals proceeds as indicated on lead 185. Finally, 
to insure that the communication lines between a satellite station and the 
central station are not indefinitely tied up due to some malfunction, the 
running of the 3 second clock, as indicated in block 182, disconnects any 
initiated communication within 3 seconds. If data has not been received 
before the expiration of such a time period, the system further is caused 
to hang up as indicated in block 194 and line 196. Alternatively, if a 
modulated carrier containing the data is detected prior to the expiration 
of that clock period, the processing of data is further enabled to proceed 
as indicated on lead 185. 
The receipt of the appropriate signals from the three clocks as indicated 
above generates a signal on lead 185 and thus causes the processing of 
data to continue as indicated in block 118, also shown in FIG. 2c. This in 
turn causes the receiving of data within the central station to begin as 
indicated in block 122. In a preferred embodiment, as indicated in block 
198, the system is enabled to detect the loss of either of the carrier 
signals, noted above. Thus, if the incoming 1600 hertz signal is lost, 
causing a dropout in received data such that the data would be improperly 
recorded, that indication is provided on lead 200 and is coupled 
therethrough to the "hang-up bus" causing the system to hang up as 
indicated in block 188 of FIG. 3a. Such a detection could be effected by a 
relay which is held in place by the 1600 hertz tone signal. Any cessation 
of the signal would cause the relay to open, thereby providing the signal 
on lead 200 as noted. Assuming that the carrier is not lost during the 
receipt of the data, processing signals continue until all data is 
received, as noted in box 202. Concomitantly with the receipt of data, the 
central station finds an open port by which data may be entered into the 
CPU, receives the reporting satellite address and advises the host CPU 
that data to be stored in the appropriate location is about to be 
transmitted, as indicated in box 204. 
Preferably, the transmission of data from each satellite station includes 
the transmission of a unique end-of-message signal at the end of each 
communication. Such an end-of-message signal corresponds to a parity check 
which may be monitored as indicated in box 206 to insure the correct 
receipt of the data. Assuming such data has been received correctly, 
instructions are then provided to enable the input of the data to the 
appropriate port of the host CPU, which has already been opened for such 
receipt, as indicated in boxes 208 and 210. Alternatively, if parity does 
not check, the satellite station is instructed to again transmit the data 
and the central station again begins to receive the data as indicated in 
box 122. Such attempts to receive data will then proceed three times as 
indicated in block 212. After three such attempts if parity still does not 
appropriately add, the system is caused to hang up as indicated on the 
"yes" output of box 212 to the "hang-up" bus on tie line 200. 
Referring now to FIG. 3c, upon completion of the receipt of the information 
within the host CPU, an acknowledgment signal is received from the CPU as 
indicated in block 142. In the event the correct receipt of the data 
within the host CPU is not acknowledged, reentry of the information into 
the host CPU is then attempted as indicated in tie line 214, box 216, and 
tie line 218 in a manner analogous to that set forth in box 212 above. If 
such attempts to enter data fail after the third attempt, the receiver of 
the central station is then instructed to open a different input port to 
the host CPU, and the data is inputted into that port, as indicated in 
boxes 220 and 222. Upon receipt of a not-acknowledged signal as indicated 
in block 224, the entry of the data into the alternative port will be 
attempted three times as indicated in block 226, thus causing the data to 
be reentered into the alternative port as indicated in line 227 and block 
222. If after three such attempts the entry of such data is still not 
verified, a signal is provided on lead 228, thus causing the CPU to 
attempt to generate an operator display and to have an auxilliary line 
printer copy the input data as indicated in block 230 of FIG. 3d. 
Upon receipt of the appropriate acknowledgment signal from either block 142 
or 224, thus indicating that the input data has been properly entered into 
the host CPU, data stored within the host CPU corresponding to the ongoing 
real time, the next required reporting time for the satellite and further 
instructions relating to that satellite's operations (identified in block 
232 as "down load data") are then outputted from the host CPU. Such data 
is then verified as indicated in block 234, and if incorrect, reentry of 
the data from the CPU is attempted three times as indicated in tie lines 
236, block 238 and line 240. If after three such attempts, the receipt of 
correct data is still not indicated, a signal is provided on lead 242 
which causes an auxilliary display monitor 243 to indicate that no data 
had been received from the host CPU. 
Assuming, however, that the data was indicated as being received correctly, 
as indicated in block 234, an acknowledgment signal "down load" data, if 
any, and an end-of-message check sum, is then transmitted to the satellite 
station as indicated in block 244. The receipt of such information within 
the satellite station then causes the transmission to the central station 
of an acknowledgment as indicated in block 246. If the acknowledgment 
indicates incorrect receipt of the information, the transmission of the 
data to the satellite station is then reattempted as indicated in tie line 
248, block 250, and tie line 252. If the acknowledgment is still not 
received after three attempts to transmit the data, the auxilliary display 
indicates that the appropriate acknowledgment was not received, as 
indicated in block 254. Concomitantly, a signal is further provided on the 
"hang-up" bus. Finally, however, assuming that appropriate acknowledgment 
was received, the central station is then caused to hang up, to clear all 
data, to reset all clocks, and to clear the input ports within the host 
CPU, as indicated in block 258, thus ending the processing as indicated in 
block 260. 
The normal sequence in which signals are transmitted between a given 
satellite station and the central station is further shown in FIG. 4, 
where all signals transmitted from the satellite station or received 
within the satellite station are shown in the upper portion of that 
figure, while that transmitted from or received by the central station are 
shown in the lower portion. In FIG. 4 it may again be seen that all 
communications start within a satellite station at the point where the 
satellite station, having recognized it has data which is appropriate to 
transmit, begins a dialing sequence such as shown in box 90 in FIG. 2b. At 
this point the dialing signal is sent from the satellite station as shown 
in region 270 in FIG. 4. When the central station picks up, causing the 
ringing signal to be terminated as indicated at line 272, the central 
station then transmits its carrier (high) signal as indicated in region 
274. The detection of that signal, indicated at line 276, then causes the 
satellite station carrier to begin. This in turn initiates a 2 second 
waiting period indicated at region 278, during which the transmission line 
settles down, after which the message is transmitted from the satellite to 
the central station as indicated at region 280. At the end of the message 
transmission period an end of transmission (E.O.T.) signal is transmitted 
as indicated at line 282, upon receipt of which, the central station 
transmits an acknowledgment signal together with ongoing time and updated 
next reporting time signals, etc. as indicated in region 284. Upon 
completion of such transmissions an end of transmission signal is 
transmitted from the central station as indicated at line 286, upon 
receipt of which the satellite station acknowledges the end of 
transmission signal as indicated in region 288. At that point the 
satellite station hangs up as indicated at line 290, thus terminating the 
transmission of the satellite carrier indicated at line 292. This in turn 
causes the central station to detect the loss of that carrier as indicated 
in zone 294, causing the central station to hang up as indicated at line 
296, thus also terminating the transmission of the central station carrier 
as indicated at line 298. 
In a preferred embodiment of the present invention, the signals involved in 
the communications between a satellite and the central station are all 
handled in a digital mode. A particularly preferred format for such 
digital signals is shown in the succession of signals set forth in FIG. 5. 
It may be seen in the top portion of FIG. 5 that a typical transmission 
from a satellite station, such as shown in the region 280 in FIG. 4, would 
first comprise a short period during which the carrier alone is sent and 
detected by the central station as indicated at region 300. Subsequent to 
that, a sync signal 302 would then be transmitted, thus enabling the 
central station and the satellite station to be synchronized with each 
other such that subsequent digital data may be properly processed. Upon 
completion of the sync signal, a "carriage return" signal 304 is 
transmitted. Thus, when the data is ultimately processed by the central 
station and caused to be outputted into an auxiliary printer display 
device or the like, the display will appropriately initiate the display of 
the next received data at the left margin of the display unit. Next, an 
identification code bit is transmitted as described hereinbelow in 
conjunction with FIG. 6. The particular identification code transmitted at 
the beginning of a given message would thus indicate that the next block 
306 identifies the satellite station then transmitting. Upon completion of 
the address code within block 306, another carriage return signal 307 
would be transmitted. Next, a second identification code 308 would be 
transmitted, the particular code being indicative of the nature of the 
actual data next to be transmitted. Accordingly, such data is then 
transmitted, as indicated in field 310, the number of bits within that 
field depending upon the type of data then being transmitted. In the 
present preferred embodiment, the particular encoding format utilized 
enables the transmission of such variable length fields. In a like manner, 
additional data will then similarly be sent, each field of data being 
initiated by a carriage return signal 312, a particular identification 
code signal 314, each again being indicative of the specific type of data 
subsequently to be transmitted, and a variable length field 316 within 
which the specific data is included. Subsequent to the last transmitted 
fields, a final carriage return signal 318 is transmitted, followed by an 
end-of-message 320, a two digit parity code 322, and an end of 
transmission 324. 
In a similar manner, as indicated in the center portion of FIG. 5, a 
typical transmission from the central station in reply to the satellite 
station transmission previously outlined above, will first consist of a 
synchronization code 330, which signal as indicated above insures that the 
satellite station and the central station are properly synchronized so as 
to insure appropriate processing of the data. Subsequently, a carriage 
return signal 332 is transmitted, followed by an acknowledgment signal 
334, which signal in turn is followed by a second carriage return signal 
336. The actual transmission of data from the central station is likewise 
initiated by an appropriate identification code signal 338, followed by 
the transmission of data within a variable length field 340. Additional 
data as necessary is then subsequently transmitted, each being preceded by 
an appropriate identification code 342 and variable length fields 344 as 
necessary. Upon completion of the transmission of the last data to be 
transmitted, a final carriage return signal 346 is transmitted, followed 
by an end of message signal 350, a two digit parity code 352, and an end 
of transmission signal 354. 
The completion of transmissions are initiated within the satellite station 
as indicated at the bottom of FIG. 5. It will there be seen that such a 
transmission includes a sync signal 356, a carriage return signal 358, an 
acknowledgment signal 360 indicating that all data has been properly 
received within the satellite station, and an end of transmission signal 
362. Upon receipt of that signal, the satellite station then hangs up as 
indicated at line 290 of FIG. 4, thus causing the satellite station to 
lose carrier, the subsequent detection of that loss of character then 
ultimately causing the central station to similarly hang up. 
FIG. 6 sets forth in more detail a typical alarm transmission message 
transmitted from a satellite station in a digitally encoded format. As is 
there shown, subsequent to the transmission of the carrier signal and a 
2-second wait 300 associated therewith, allowing the communication network 
to "settle-down", a sync signal 302 is transmitted, as is also indicated 
in FIG. 5. Subsequent to the transmission of a carriage return signal 304, 
an identification code 305 is then transmitted, the particular code being 
indicative of the data next to be transmitted. Each identification code is 
desirably a unique alphabetic letter, the particular letter being selected 
to provide a mnemonic representation of the particular type message next 
to be transmitted. The following identification codes, while preferable, 
are exemplary of various identification codes which may be used: 
A--Alarm 
B--Battery Dying 
C--Close - store closing 
I--Satellite Address number 
L--Low battery capacity 
O--Open - store open 
P--Phone # (see note) 
R--Restore 
S--Schedule Change 
T--Trouble 
Z--Close w/Zone out 
D--No. of Dial Attempts (1-8) 
As indicated in FIG. 6, the use of the identification code I in Block 305 
thus indicates that the next data to be transmitted identifies the given 
satellite then in communication. As is indicated in the next series of 
blocks 364, the given satellite then in communication would have the 
address number 7777. The end of that transmission is followed by a 
carriage return signal 366. The next series of data is again initiated by 
a field identification code 368 in which the letter D signifies that the 
data next being transmitted is indicative of the number of dialing 
attempts that the current transmission represents. The specific number 
then being attempted is indicated at block 370. After eight unsuccessful 
attempts, the satellite station will "go to sleep" for 30 minutes and will 
then try again, this cycle being continued until an acknowledgment signal 
is ultimately transmitted from the central station. The completion of that 
signal is again indicated by a carriage return signal 372, followed by 
another field identification signal 374, in this instance, the letter A 
indicating an actual alarm situation. The subsequent blocks 376, 378, 380, 
382, 384, 386, 388 and 390 thus indicate that an alarm has occurred in 
loop No. 3, zone 7, at the particular week, day, hour and minutes there 
specified. The completion of such an alarm signal is then indicated by a 
carriage return signal 391 as described hereinabove. The next data 
transmitted is again indicated by a field identification code 392, the 
letter C indicating a "store closing". The next 5 digit block, 394, is 
thus indicative of the week, day, hours and minutes at which the store 
closing signal was transmitted. The completion of that data block is again 
indicated by a carriage return signal 396 and the initiation of the next 
data block again indicated by another field identification code 398. Such 
a sequence of data transmissions continues as indicated in the general 
region 400 until all data previously stored or available for transmission 
from the satellite station has been transmitted. Upon completion thereof 
an end of message signal 320, parity check code 322, and end of 
transmission signal 324, respectively, are then transmitted as indicated 
in FIG. 5. 
In analogous fashion, a typical time update response from the central 
station is set forth in FIG. 7. It may there be seen that such a 
transmission begins, as indicated above, with a sync signal 404. Such a 
signal is followed by a carriage return signal 406 and an acknowledgment 
signal 408 which thus indicates to the satellite station that its previous 
transmissions have been appropriately received. This is in turn followed 
by an additional carriage return signal 410, which in turn is followed by 
an identification code unique to the type of data being transmitted from 
the central station. For example, such codes would include the following: 
K--Set clock time 
V--Primary phone # 
Q--Secondary phone # 
E--Next report time 
Thus, as indicated in FIG. 7, a first field identification code K in block 
412 would indicate that the data next to be transmitted is to be utilized 
by the satellite station to set the local clock within that satellite. As 
there indicated, the on going time would thus be week--0, day--4, hour 
and minutes 0043, respectively, as indicated in the grouped block 414. 
Upon completion an additional carriage return signal 416, end of message 
signal 418, parity signal 420, and end of transmission signal 422 would 
then be transmitted. As may readily be recognized, a similar transmission 
indicating the next required reporting time would be preceded by a field 
identification No. E, followed by the appropriate digitally encoded time 
information. 
In like fashion, a typical response from the central station instructing 
the satellite station to change its primary telephone number is set forth 
in FIG. 8. Such a transmission again is initiated by a sync signal 424, 
followed by carriage return signal 426 and acknowledgment signal 428 and 
additional carriage return signal 430. The next field identification code 
V in block 431 is thus indicative of a primary telephone number. A fixed 
field 432 which is 30 digits long then follows which represents a 15 digit 
telephone number, right justified (blocks 434) followed by an additional 
15 digit sequence (blocks 436) in which the same number is set forth in 
hexadecimal reciprocal reverse order. Upon completion of such a fixed 
field, the end of the message is again indicated by the end-of-message 
signal 350, a 2-digit parity signal 352, and the end of transmission 
signal 354. 
It may thus be seen that the sequence of transmissions between a given 
satellite station and the central station may be varied depending upon the 
specific data to be transmitted and the desired encoding formats utilized. 
Accordingly, variations of conventional encoding formats, alarms and other 
signal sources and the like may similarly be utilized. 
Under typical conditions an industrial or a commercial establishment might 
have two or three non-routine transmissions in a year's time. These might 
include a true burglary, a false alarm (caused by people or equipment), a 
failing battery, etc. The preponderance of data is routine, such as the 
normal opening and closing time of the establishment. The management of 
the establishment may wish to know when the actual openings and closings 
occur, but it is not necessary that the Central Station know as they 
happen (i.e., in real time). This then allows this routine data to be sent 
to the Central Station at predetermined times so as to space the traffic 
uniformly throughout the day. Conventional "interrupt only" systems that 
function in real time create a traffic loading problem at `peak` times of 
the day; much in the same way as electric power utilities experience peak 
demands. Capital equipment expenditures are based on peak demand. The 
system described herein allows distribution of the demand thus lowering 
the cost of telephone lines, computers, and personnel, with plenty of time 
interspersed to handle the very low percentage of non-routine signals. 
In the specific embodiment described hereinabove, each satellite station 
contains a single chip microcomputer such as type 1802 manufactured by RCA 
Corp., which includes as an integral part thereof, the functions of 
memory, I/O, central processors, local clock, and the like. In like 
fashion, the receiver and transmitter of each satellite station are 
contained within a single-chip MODEM, such as type MC14412 manufactured by 
Motorola Semiconductor Products, Inc. In contrast, the central station 
consists of a receiver-transmitter made from the Motorola Micromodule 
System. That is interfaced to a Tandem, Inc. model 16 computer which 
contains the host CPU, memory and master clock.