Notification apparatus for outbound data communication system

A time independent, data communication system via non-dedicated telephone transmission lines, to remotely notify a local computer to dial out to a data network is disclosed. The local computer dial out is initiated if the telephone connected to the local telephone transmission line is not in use at a predetermined time period, or time range after a predetermined time period, after a ring is detected. In a preferred embodiment, a retriggerable timer is activated by a ring detector circuit. After the timer tines out, if a hook detector circuit detects the telephone transmission line is in an on-hook condition, the local computer dial out is initiated.

BACKGROUND 
1. Field of the Invention 
The present invention relates generally to telephone data communication 
systems, and more particularly to time independent data communication 
systems via non-dedicated telephone transmission lines, to remotely notify 
a local computer to dial out to a data network. 
2. Description of the Prior Art 
Various systems are presently known which provide remote notification to 
local computers or data sets via non-dedicated telephone transmission 
lines. 
In the U.S. Pat. No. 4,085,292 to Leslar (1978) and U.S. Pat. No. 4,232,195 
to Bartelink (1980), calls are automatically answered and tones are 
generated to indicate the condition of the local data set. In the U.S. 
Pat. No. 3,902,016 to Blouch (1975), U.S. Pat. No. 4,345,113 to Shelley 
(1982), and U.S. Pat. No. 5,490,210 to Sasso (1996), calls are 
automatically answered and tones are sensed to selectively activate 
devices or permit normal telephone operation. In the U.S. Pat. No. 
4,086,438 to Skidmore (1978), calls are automatically answered and tones 
are sensed to selectively dial out to other numbers. In the U.S. Pat. No. 
4,922,521 to Krikke (1990), calls are automatically answered by the local 
computer and the caller transmits an identification number. If the number 
is authorized, the line is released and the local computer dials back to 
the caller. 
It is preferable that the call is not answered so that there is not an 
additional charge for the call. 
In the U.S. Pat. No. 3,783,193 to Lee (1974), U.S. Pat. No. 3,876,836 to 
Langan (1975), U.S. Pat. No. 4,654,868 to Shelley (1987), and U.S. Pat. 
No. 4,995,109 to Arizumi (1991), predetermined sequences of rings are 
detected to selectively activate devices. 
It is preferable to avoid dependence on counts of rings or sequences of 
rings because it is difficult to precisely determine when to hang up the 
remotely initiated call to cause a precise number of rings to occur on the 
local telephone transmission line, particularly if the mechanism is to be 
used with varied types of transmission line systems, such as 
geographically diverse public switched telephone networks. 
In the U.S. Pat. No. 4,126,762 to Martin (1978), in one embodiment a 
predetermined time window is utilized. In another embodiment, sequential 
ringing signals, having a different time spacing than signals from a 
normal telephone call activate the local data set. In the U.S. Pat. No. 
4,355,205 to Walker (1982), a coded signal is transmitted between the 
first and second ring. In the U.S. Pat. No. 5,361,296 to Reyes (1994), a 
modem is configured to sense distinctive ring types to perform selective 
processing of the call. In the U.S. Pat. No. 5,416,831 to Chewning (1995) 
and U.S. Pat. No. 5,635,980 to Lin (1997), a coded Analog Display Service 
Interface (ADSI) signal is sensed while the telephone is on-hook to 
selectively control devices. 
It is preferable to avoid dependence on characteristics, such as 
alternative time-spacing of rings, distinctive ring types or signals 
sensed or transmitted while on-hook, that may not be available on all 
telephone transmission line systems, or may only be available at 
additional cost. It is also preferable that the local computer be 
accessible at all times, rather than only during a predetermined time 
window. 
In the U.S. Pat. No. 4,578,534 to Shelley (1986), the data set is normally 
connected and the telephone is normally disconnected. The termination of 
the ringing signal after a predetermined number of ring bursts causes the 
data set to begin to communicate with the central computer. If additional 
ring bursts occur, a non-computer call is sensed and the data set is 
disconnected and the telephone connected to the telephone transmission 
line so that normal telephone usage is allowed. 
It is preferable to connect the local computer and notification apparatus 
in parallel with other telephone devices to avoid the need for a 
particular configuration of telephone transmission line wiring. 
In the U.S. Pat. No. 5,235,634 to Oliver (1993), if the number of rings 
counted on a particular call exceeds a predetermined number of rings, then 
the device is activated to seize the telephone transmission line, dial the 
predetermined telephone number and transmit collected data from the site 
over the telephone transmission line to the central host. 
It is preferable to use the subscriber's existing telephone transmission 
line rather than install a separate dedicated line to provide access to 
the local device. It is preferable to avoid reliance on a maximum number 
of rings to avoid interfering with normal use of the subscriber's 
telephone. If the predetermined number of rings is small, normal telephone 
calls, as well as those for remote notification purpose, will trigger the 
device. If the predetermined number of rings is larger, and the subscriber 
is available, he is likely to answer a remotely initiated call intended 
only for notification of the local device, and his answering it may 
preclude the additional rings necessary for triggering the device. If the 
subscriber is not available but an automatic answering apparatus, such as 
a telephone answering machine or fax machine, is employed, it may 
automatically answer a remotely initiated call and preclude the additional 
rings necessary for triggering the device. It is also preferable to that 
the remotely initiated call is not answered so that there is not an 
additional charge for the call. 
Accordingly, the need exists for a system that allows a remote notification 
to a local computer via non-dedicated telephone transmission lines at any 
time (i.e. no limitation to a time window). Furthermore, such a system 
should allow normal operation of the telephone. Furthermore, the remotely 
initiated calls and calls from outside callers should not be answered by 
the local computer or notification apparatus, to avoid additional charges 
for calls when the telephone is unanswered by the subscriber, for example. 
Furthermore, such a system should not rely on counts of rings or sequences 
of rings because it is difficult to precisely determine when to hang up 
the remotely initiated call to cause a precise number of rings to occur on 
the local telephone transmission lines, particularly if the mechanism is 
to be used with varied types of transmission line systems, such as 
geographically diverse public switched telephone networks. Furthermore, 
such a system should not rely on alternative time-spacing of rings, 
distinctive ring types or signals sensed or transmitted while on-hook, 
because these features may not be available to all subscribers or may only 
be provided at additional expense. Furthermore, the local computer and 
notification apparatus should connect in parallel with other telephone 
devices and there should be no requirement to modify the telephone 
transmission line wiring to the primary or secondary telephones. 
OBJECTS AND ADVANTAGES 
It is therefore an object of the present invention to provide an improved 
data communication system, that enables remote notification, at any time, 
to a local computer to initiate a connection to a data network. 
It is a further object of this invention to provide data communication 
system, via non-dedicated telephone transmission lines, that allows normal 
operation of the telephone by the subscriber. 
Another object of the invention is to avoid the need for the local computer 
or notification apparatus to answer remotely initiated notification calls 
and calls from outside persons intended for the subscriber, to avoid 
additional charges for calls when the telephone is unanswered by the 
subscriber, for example. 
A further object of the invention is to avoid dependency on counts of rings 
or sequences of rings to avoid the requirement of timing the hang up of 
the remotely initiated call to cause a precise number of rings to occur on 
the local telephone transmission lines. 
A still further object of the invention is to avoid dependency on 
alternative time-spacing of rings, distinctive ring types or signals 
sensed or transmitted while on-hook. 
A yet further object of the invention is to connect in parallel with other 
telephone devices to avoid modification to the telephone transmission line 
wiring to the primary or secondary telephones. 
Other objects, features, and advantages of the present invention will be 
apparent from a consideration of the drawings and ensuing description.

SUMMARY 
In accordance with the present invention, at a predetermined time or during 
a predetermined time range after a ring is detected on a telephone 
transmission line, the hook condition of the telephone transmission line 
is detected and if the telephone transmission line is not in use, a local 
computer dials out to a data network. 
DESCRIPTION 
The notification system is used in conjunction with a telephone 
transmission line. In the preferred embodiment, the system is connected to 
a plain old telephone service (POTS) single line system via the tip 
connector 1 and ring connector 2 connected to a ring detector circuit 3 
and a hook detector circuit 9 (FIG. 1). The ring detector circuit 3 
detects ring voltages greater than 80 VAC. When such voltages occur, the 
ring detector 3 transmits one or more low-level voltage pulses on output 
line 12. When no such voltage conditions occur, the ring detector 
maintains a high-level voltage output line 12. The output line 12 is 
connected to the retriggerable timer circuit consisting of NE555 timer 4, 
capacitor 5, resistor 6 and transistor 7. 
The NE555 timer normally transmits a low-level voltage on output line 13. A 
low-level voltage pulse on line 12 triggers the NE555 timer causing it to 
transmit a high-level signal on output line 13 and to begin charging the 
capacitor 5 through resistor 6. The capacitor and resistor are configured 
such that the capacitor voltage will reach the NE555 timer threshold 
voltage after a time delay period of 15 seconds. In the preferred 
embodiment, the capacitor has a value of 10 uF and the resistor a value of 
1.5 Meg-ohms. When the capacitor voltage reaches this threshold, the NE555 
timer 4 times out and transmits a low-level signal on output line 13. 
In the preferred embodiment, if subsequent rings are detected, the ring 
detector circuit transmits subsequent low-level voltage pulses on line 12. 
If a low-level voltage is present on line 12 while the capacitor 5 is 
charging, the relatively low voltage on the base of transistor 7 causes 
the capacitor to discharge through the transistor, resetting the time 
delay period. When a high-level voltage is present at the base of 
transistor 7, the capacitor resumes charging. When ringing ceases, a 
high-level voltage on line 12 is continuously maintained, and the 
capacitor reaches the threshold voltage after a subsequent time delay 
period of 15 seconds. In another embodiment, transistor 7 is omitted and 
the capacitor 5 is not discharged during subsequent rings so that the 
capacitor 5 charges to the threshold voltage after a time delay period of 
15 seconds after the first ring. 
The hook detector circuit 9 detects the voltage differential between the 
tip connector 1 and ring connector 2. The hook status is defined as 
on-hook when the voltage differential is greater than 24 volts, and 
off-hook when such voltage differential is less than 24 volts. The hook 
detector circuit transmits a high-level voltage on output line 14 while an 
on-hook condition is detected and transmits a low-level voltage on output 
line 14 when an off-hook condition is detected. Output line 14 is 
connected to the J input of flip-flop 10. 
Output line 13 is connected to the clock input of flip-flop 10. Output line 
12 is connected to the reset input of flip-flop 10. When a low-level 
voltage is present on output line 12, the flip-flop transmits a low-level 
voltage on output line 18. The flip-flop will continue to transmit a 
low-level voltage on output line 18 until a high-level voltage is present 
on output line 12, indicating the absence of a ring burst, a high-level 
voltage is present on output line 14, indicating an on-hook condition, and 
output line 13 transitions from a high-level voltage to a low-level 
voltage, indicating the time delay period has elapsed. When all three 
conditions occur simultaneously, the flip-flop will transmit a high-level 
voltage on output line 18. 
Output line 18 is connected to local computer 11, such as a personal 
computer, mainframe computer, computer-based telephone, or information 
appliance. The local computer monitors the voltage on output line 18. A 
transition on output line 18 from low-level voltage to high-level voltage 
causes the local computer to dial out to a data network. 
Another embodiment omits flip-flop 10 and includes timer 17, resistor 16, 
capacitor 15, and "AND" gate 19 (FIG. 2). The timer 17 normally transmits 
a low-level voltage on output line 20. A low-level voltage pulse on line 
13 triggers the timer 17 causing it to transmit a high-level signal on 
output line 20 and to begin charging the capacitor 15 through resistor 16. 
The capacitor and resistor are configured such that the capacitor voltage 
will reach the timer 17 threshold voltage after a time delay period of 20 
seconds. In the preferred embodiment, the capacitor has a value of 10 uF 
and the resistor a value of 2.0 Meg-ohms. When the capacitor voltage 
reaches this threshold, timer 17 times out and transmits a low-level 
signal on output line 20. Output line 20 is connected to "AND" gate 19. 
Output line 14 from hook detector 9 is also connected to "AND" gate 19. 
"AND" gate 19 transmits a high-level voltage on output line 22 if both 
output line 14 is at a high-level voltage, indicating an on-hook 
condition, and output line 20 is at a high-level voltage, indicating the 
timer 17 has triggered but the time delay period has not yet expired, 
otherwise "AND" gate 19 transmits a low-level voltage on output line 22. 
Output line 22 is connected to local computer 11. The local computer 
monitors the voltage on output line 22. A transition on output line 22 
from low-level voltage to high-level voltage causes the local computer to 
dial out to a data network. In another embodiment, transistor 7 is omitted 
and the capacitor 5 is not discharged during subsequent rings so that the 
capacitor 5 charges to the threshold voltage after a time delay period of 
15 seconds after the first ring. 
The preferred embodiment for the ring detector 3 and hook detector 9 
circuits is illustrated in FIG. 3. Tip connector 1 is connected through 
resistor 31 to bias resistors 32 and 33 and to the negative input of LM339 
voltage comparator 30. Ring connector 2 is connected through resistor 34 
to bias resistors 35 and 36 and to the positive input of voltage 
comparator 30. The bias resistors are configured to so that the voltage 
differential is indicative of a ring burst being present on the telephone 
transmission lines. When a ring burst is present, the voltage comparator 
30 transmits a low-level voltage on output line 12, and when absent, 
transmits a high-level voltage on output line 12. 
Tip connector 1 is also connected through resistor 41 to bias resistors 42 
and 43 and to the positive input of voltage comparator 40. Ring connector 
2 is also connected through resistor 44 to bias resistors 45 and 46 and to 
the negative input of LM339 voltage comparator 40. The bias resistors are 
configured to so that the voltage differential is indicative of the on/off 
hook condition present on the telephone transmission lines. When a primary 
or secondary telephone connected to the telephone transmission lines is 
off-hook, the voltage comparator transmits 40 a low-level voltage on 
output line 14, and when all primary and secondary telephones connected to 
the telephone transmission lines are on-hook, transmits a high-level 
voltage on output line 14. In another embodiment, the hook detector 
circuit is implemented as part of the telephone and detects the condition 
of the telephone's physical hook-switch. In another embodiment, the hook 
detector circuit is implemented as a circuit that detects the presence or 
absence of a dial tone or other tones or other sounds. 
In one embodiment this notification apparatus is a standalone device 
coupling the telephone transmission line to the local computer. In another 
embodiment this notification apparatus is implemented as a component of 
the local computer, such as a personal computer, mainframe computer, 
computer-based telephone, or information appliance. In another embodiment 
this notification apparatus is implemented as a component of the local 
telephone. 
CONCLUSION, RAMIFICATION, AND SCOPE 
Accordingly, the reader will see that the present invention provides a data 
communication system with several advantages which include: 
enabling remote notification, at any time, to a local computer to initiate 
a connection to a data network. 
connection via non-dedicated telephone transmission lines, that allows 
normal operation of the telephone by the subscriber. 
avoiding the need for the local computer or notification apparatus to 
answer remotely initiated notification calls and calls from outside 
persons intended for the subscriber, to avoid additional charges for calls 
when the telephone is unanswered by the subscriber, for example. 
avoiding dependency on counts of rings or sequences of rings to avoid the 
requirement of timing the hang up of the remotely initiated call to cause 
a precise number of rings to occur on the local telephone transmission 
line. 
avoiding dependency on alternative time-spacing of rings, distinctive ring 
types or signals sensed or transmitted while on-hook. 
connecting in parallel with other telephone devices thus avoiding 
modification to the telephone transmission line wiring to the primary or 
secondary telephones. 
The present invention finds application in many areas in which connection 
to the data network is via outbound rather than inbound calls, such as 
standard internet service providers and online information systems, as 
well as applications where it is preferable for the call to be charged as 
dialed by the local computer rather than, or in addition to, being dialed 
remotely. One such area, for instance, might be notification that 
electronic-mail, fax, page or other communique has been received by a 
remote computer, so that the local computer can retrieve it promptly. 
Another area might be notification of an event, for instance, an event 
monitored by a filter or agent program, such as a particular stock price 
reaching a predetermined level or the availability of a particular product 
or service, so that the local computer may report it promptly. Still 
another area might be notification that a person wishes to communicate to 
the user of the remote computer via text chat, voice, video, or other 
medium transmitted via the data network, so that the local computer may 
receive it and reply promptly. Yet another area might be notification that 
a remote computer wishes to configure or poll the local computer or 
devices attached to the local computer, such as lights or appliances. 
Although the invention is described for use with telephone transmission 
lines, it will be apparent to one skilled in the art that the invention 
can also be used with transmission media other than telephone transmission 
lines. 
Although the description above contains many specificities, these should 
not be construed as limiting the scope of the invention but as merely 
providing illustrations of some of the presently preferred embodiments of 
this invention. It will, however, be evident that various modifications 
and changes may be made thereunto without departing from the broader 
spirit and scope of the invention as set forth in the appended claims. 
Many variations are possible. For example, the time period for each of the 
timers may vary from a very short period to an indefinitely long period. 
Also the circuit may be implemented using discrete components or custom 
integrated circuits or programmable logic or computer circuits. Thus the 
scope of the invention should be determined not by the embodiments 
illustrated, but by the appended claims and their legal equivalents.