Dual signal triggered message waiting notification system for indicating storage of different types of messages awaiting retrieval

A message waiting notification system comprising a telephone provider's off premise central switching office connected to a Dual Signal Triggered Message Waiting Indicator (DSTMWI) circuit via a telephone line is disclosed. The central switching office transmits predetermined asynchronous Frequency Shift Keying (FSK) signals and/or audible tones indicating different types of electronically stored communication messages awaiting retrieval, such as voice mail, E-mail, fax mail and video mail. Responsive to receiving the FSK signals and/or audible tones from the central switching office via the telephone line, the DSTMWI circuit provides visual notification of any combination of different types of the electronically stored communication messages.

BACKGROUND 
1. Field of Invention 
This present invention relates to a unique Message Waiting Indicator (MWI) 
circuit and, more particularly to such an indicator circuit that is 
triggered by either an asynchronous Frequency Shift Keying (FSK) digital 
word/words and/or an audible tone signal as sent via a telephone line from 
a telephone service provider's off premise central switching office. 
2. Description of Prior Art 
With the development of the digital storage of voice messages in a computer 
system for future listening, known as Voice Mail, various arrangements 
have been developed for notifying Voice Mail users of stored messages 
awaiting retrieval. Presently, to alert a subscriber that a message is 
waiting, a light at a telephone is triggered via a signal to indicate the 
presence of a message. Several methods are used for illuminating such a 
lamp. 
Prior art has focused on using a message waiting indication (MWI) voltage 
to trigger a lamp for analog telephones such as that described in U.S. 
Pat. No. 3,532,832 issued to, Hestad et al on Oct. 6, 1970 and in U.S. 
Pat. No. 4,648,109 issued to Boeckmann on Mar. 3, 1987. Recent 
advancements have allowed the signal to be sent via an FSK signal as 
referenced in U.S. patent application Ser. No. 08/221,863 of the 
applicants herein, filed Mar. 31, 1994 (abandoned), and through the 
detection of a call progress tone signal. 
U.S. Pat. No. 5,327,493 issued to Richmond et al on Jul. 5, 1994 describes 
a device and method for detecting call progress tones which device then 
causes other actions, mainly the illumination of an indicator light on 
equipment connected to a telephone line. This invented device 
automatically and periodically goes "off-hook", listens for a dial tone 
and determines whether it is a special dial tone. With the presence of the 
tone, the light is illuminated. 
This device, as presented by Richmond et al, fails to address the problem 
of central office switch overload by repetitive "off-hook" polling for the 
absence or presence of the call progress tone. Our invention will provide 
a means of minimizing this concern by allowing the automatic off hook 
detection for an audible tone to be turned off. 
Previous art also fails to address the need for one device to provide 
calling party Caller Identification (Caller ID) capabilities and Voice 
Mail message waiting notification using broken dial tone detection 
circuitry. Previous art requires the end user of Voice Mail using broken 
dial tone detection and Caller ID services to install two pieces of 
equipment on their telephone line: one unit to receive the Caller ID 
number and another to receive the message waiting notification. 
To meet the widely perceived need for an indication that a message is 
waiting retrieval, prior art has addressed methods of triggering an 
indicator light with separate and distinct pieces of equipment dependent 
upon the signal delivered. However, "broken dialtone", i.e., stutter 
dialtone, FSK signaling, MWI voltages, and other special electronic 
signals can be delivered by the same central office telephone switch or 
Private Branch Exchange (PBX) equipment. These prior arts fail to allow a 
telephone switching equipment to provide varying types or more than one 
type of signal to trigger a visual indication on a single device connected 
to the telephone line. With prior art the signal delivered becomes 
dependent on the telephone system and the type of listening device 
attached to the telephone. 
Additionally, each of these prior arts are limited to the notification of 
one type of stored message, usually a voice mail message. With the even 
more recent development of the computer capabilities to store voice mail 
messages, fax mail messages, electronic mail messages and video mail in 
one database, each of these mediums will require the notification of the 
user of the type of mail stored. The different types of signals could be 
used to indicate the different types of messages that can be stored. Prior 
art has not addressed this concern. 
Prior Caller ID art does not address the need to have message waiting 
notification in combination with the calling party's number display 
screen. Any type of incoming notification signal may be combined with the 
Caller ID technology to provide an economical and practical solution over 
two pieces of equipment. 
OBJECTS AND ADVANTAGES 
Accordingly, an object of the invention is to provide new and improved Dual 
Signal Triggered Message Waiting Indicator (DSTMWI) systems. Several 
objects and advantages of our invention are: 
(a) to provide an intelligent circuitry that utilizes either asynchronous 
FSK encoded digital words/word and/or call progress tones to turn on one 
or more lamps to notify a user of the presence of one or more different 
types of electronically stored messages; any type. 
(b) a device using the intelligent circuit of (a) that utilizes a switch to 
disable the off-hook polling of call progress tones circuitry to minimize 
central office switch overload; 
(c) a device using the intelligent circuit of (a) that will turn on a lamp 
in response to detecting an audible tone, such as DTMF tones, as sent via 
a telephone line; and 
(d) an enclosure to house the circuitry of (b) or (c) that will provide 
substantially increased visibility due to its design allowing a lamp 
manufacture's viewinq angle rating to be increased. 
Further objects and advantages of my invention will become apparent from a 
consideration of the drawings and ensuing descriptions. 
SUMMARY OF THE INVENTION 
One aspect of the disclosed invention is the conversion of a telephone 
switch initiated signal to visual indications. An embodiment of this 
invention illuminates a visual indication light on a device connected to 
the customer's telephone line when either an auditory message waiting 
indication in the form of a non-standard dial tone or a FSK signal is 
placed on the customer's line by the central office. This embodiment of 
the invention overcomes the short comings of the current message waiting 
indication systems previously described. It is far less expensive; the 
message waiting indication detector and indicator light can be added to 
the customer's telephone equipment without replacing existing equipment; 
Additionally, neither the voice mail user nor the telephone service 
provider needs to distinguish what type of signal to send to a voice mail 
user. This minimizes confusion in the marketplace of what type of unit is 
required by the end user. 
If an auditory message waiting indication is delivered this will not 
interfere with the other signals, and the auditory indication can still be 
heard at all extension telephones. If both an auditory indication and a 
FSK signal are delivered, the customer's telephone can be "off-hook" for 
any number of hours and it can deliver the notification signal as the 
broken dial tone is not lost after a set amount of time. (FSK signaling 
resets after 21/2 hours.) 
In other applications, the signaling can take the form of DTMF (dual tone 
multi frequency) tones instead of a distinctive non-standard dial tone. 
The ring or off hook of the telephone acts as the initiation clock to 
notify the device to go off hook to listen for the DTMF tone. The 
signaling method may take the form of any type of audible tones 
transmittable over the telephone line. The inventions detection circuity 
can be programed to recognize these designated tones to trigger on/off the 
indicator light. 
Another aspect of the invention is a novel method of using more than one 
type of signal or different forms of the same signal (ie. different DTMF 
tones) to indicate different types of electronically stored messages. A 
FSK signal could indicate voice mail messages stored, a DTMF signal 
indicates a fax mail message stored, and a call progress tone a stored 
e-mail message. 
An alternative embodiment allows for a three position or toggle switch to 
turn off the broken dial tone detection function when it is not needed. 
Central office switches can be adversely affected with switch overload by 
devices that automatically go off-hook to listen for a call progress tone 
as presented in prior art. If FSK signaling is used in a territory where 
broken dial tone detection is undesirable, this feature can be disabled 
with the switch. It is also possible to temporarily disable the broken 
dial tone detection if the voice mail service is temporarily discontinued. 
Accordingly the invention can be configured to take various positions as a 
user may want to disable E-mail storage but not voice mail storage 
notification. Any combination of alternatives can be envisioned. 
Another embodiment allows user of Caller ID service to also have call 
progress tone detection for Voice Mail services without requiring an 
additional piece of equipment. Again the broken dial tone detection could 
be turned off without turning off the Caller ID capabilities. 
Although the description above contains many specifications, these should 
not be construed as limiting the scope of the invention but merely 
providing illustration of some of the presently preferred embodiments of 
this invention.

DESCRIPTION OF PREFERRED EMBODIMENT 
FIG. 1 is a block diagram of the DSTMWI. FSK receiver l00, clock 200, 
serial decoder 300, and notification latch 400 describe the FSK portion of 
the DSTMWI. Line interface 600, logic circuit 700, timing circuit 800, and 
tone detect circuit 900 describe the broken dial-tone detect portion of 
the DSTMWI. OR gate 1000 sums the two outputs of the FSK and stutter MWI 
detectors to give a combined MWI signal to notification means 1100. Power 
supply 500 provides the necessary voltages for all portions of the 
circuit. Stutter tone detect disable switch 1200 disconnects the telephone 
line to the stutter portion of the DSTMWI. This gives the option of not 
having the unit poll the telephone line when FSK MWI is available, thus 
reducing network loading. 
As shown in FIG. 2, the front end of the FSK portion consists of standard 
circuitry of any form of FSK receiver 100 typically comprising; input 
amplifier/buffer /limiter circuit 101 followed by bandpass filter 102, 
followed by demodulator 104. The outputs of this circuit are a carrier 
detect and a data output. The carrier detect output goes high whenever an 
FSK `space` or `mark` tone is present on the telephone line. The data 
output logic level is dependant on whether the FSK tone is a `space` or 
`mark`. This output gives the serial digital data as represented as FSK 
tones on the telephone line. If the tone is a `mark`, the data output is a 
high or logical 1. If the tone is a `space` then the data output is a low 
or logical 0. 
The FSK receiver 100 outputs drive the serial decoder circuit 300 that 
compares an incoming FSK data stream to predetermined digital codes that 
represent the need to turn ON or OFF any of the notifier devices. The 
first eight bits of the incoming FSK data stream are compared to two 
different predetermined key data word 330A and 330B. If there is a match, 
then either comparator 328A or 328B' S output will be high, turning `ON` 
or `OFF` the notification means 1100 via OR gate 1000. Thus, FSK data code 
determines the status of any number of indicators. 
A high on demodulator 104' s carrier detect output resets shift register 
326 and set/reset flip-flop 320 through 1-shot multivibrator 318. 
Set/reset flip-flop 320 holds off clock 200 with AND gate 322 until the 
first `start` data bit appears on data line from demodulator 104. This 
`start` bit sets set/reset flip-flop 320 output high, which puts clock 200 
output into the clock input or divider 324. This divider is chosen to have 
an output that is timed appropriately for the timing baud rate of the FSK 
protocol used. The output of divider 324 goes to shift register 326 clock 
input, effectively `clocking` in the incoming data stream. The `N` of 
divide by `N` counter 332 is chosen based upon the length of the data 
stream expected to contain the information that turn ON or OFF the FSK 
message waiting notifiers. Shift register 326, comparators 328A and 328B, 
key data words 330A and 330B, and divide by `N` counter 332 can be of any 
length desired. 
More than two comparators (328A & 328B) and key data words (330A & 330B) 
can be connected and compared to shift register 326 if multiple notifiers 
are desired. Multiple notifiers could be used to indicate the status of 
stored voice messages, FAX messages, E-mail, video mail, etc. Multiple 
words could be used or just a single eight bit word read into shift 
register 326 could determine the status of eight different notifiers. 
The output of AND gate 334A or 334B will go high when the length of the 
data stream is reached (as determined by the divide by `N` counter 332), 
and comparator 328A or 328B output is high indicating a match between key 
data word 330A or 330B to the contents of shift register 326, and the 
carrier detect input is still high indicating FSK tones are being received 
and data is likely to be valid. 
Since notifier status outputs from AND gates 334A or 334B will only be high 
for a short period of time, set/reset notification latch 400 is needed to 
keep the notifier ON or OFF until another FSK signalled command is sent 
from the off premise central switching office. The output of notification 
latch 400 provides the input logic to notification means 1100. 
FIG. 3 shows the circuit comprising the line interface 600 of the broken 
dial-tone portion of the DSTMWI. Bridge 602 ensures proper polarity for 
off-hook FET 604. Ring detection is accomplished by tip/ring voltage 
rising above zener 606 voltage making output of comparator op-amp 608 go 
high. Capacitor 610 provides filtering to make the ring detect output a 
constant DC level. Off-hook detect is accomplished by detecting a low 
tip-ring voltage through resistor divider 612 and 614, driving schmidt 
trigger inverting buffer 616 high. Diode 618 ensures that off hook detect 
output does not go high when off-hook FET 604 is enabled. Analog output 
for tone detect is accomplished by measuring voltage across off-hook load 
resistor 620. 
FIG. 4 shows the logic circuitry 700 of the broken dial-tone portion of the 
DSTMWI. If an off-hook condition occurs, latch 702 is set. If a ring 
occurs, latch 704 is set. Either occurrence will reset timing circuit 800 
via diodes 726 and 728. If the one minute signal from timer 800 goes high, 
and an off-hook condition has occurred as indicated by set latch 702, then 
gate 706 output goes low. If the three minute signal from timer 800 goes 
high, and a ring has occurred as indicated by set latch 704, then gate 708 
output goes low. If either gate 706 or 708 gate goes low, then output of 
gate 710 goes high, turning on off-hook FET 604 of line interface circuit. 
If neither off-hook or a ring has occurred, the off-hook output signal 
will go high when the 12 minute signal from timer 800 goes high, via diode 
712. Any time the off-hook signal goes high, a three second reset delay is 
accomplished via resistor 716, capacitor 718, and schmidt trigger 
inverters 720 and 722. This part of the circuit performs the logic circuit 
and timing circuit reset signal after the poll for broken dial-tone 
(off-hook is high), has occurred for three seconds. The beginning of the 
poll resets notifier enable latch 732 and stutter dial tone counter 734 
via capacitor 730. When four stutters have been clocked into counter 734 
via the dial-tone detect circuit 900, then the Q2 output of counter 734 
goes high, setting notifier latch 732. Set notifier latch 732 enables 
notifier strobe schmidt trigger gate 736 providing an on/off pattern of 
notification. Resistor 738 and capacitor 740 provide the timing for the 
on/off cycling. 
FIG. 5 shows the timing circuit 800 of the broken dial-tone portion of the 
DSTMWI. Op-amp 802 provides the clock circuit. Positive feedback is 
obtained through resistors 804 and 806, while clock timing is obtained 
through resistor 808 and capacitor 810. The output of the clock op-amp 802 
drives the clock input of counter 812, providing one minute, three minute 
and 12 minute output signals to drive logic circuit 700. Clock reset is 
accomplished by forcing the voltage on timing capacitor 810 high through 
isolation diode 814. 
FIG. 6 shows the tone detect circuit 900 of the broken dial-tone portion of 
the DSTMWI. Band-pass amplification is accomplished with op-amp 902 and 
bandpass/amplifier capacitors 904 and 906, and resistors 908, 910, and 
912. The frequency can be set to any of the individual frequencies that 
make up a dial tone. Using a bandpass filter helps to eliminate any false 
MWI triggering that might occur when the unit goes off-hook and encounters 
excessive noise on the telephone line. An averaging circuit comprised of 
diode 914, capacitor 916 and resistor 918 creates a DC level when a 
constant dial-tone is encountered and a varying level when a stuttered 
dial-tone is encountered. Schmidt trigger inverter 920 cleans up this 
possible varying signal to provide clean transitions for the stutter 
dial-tone counter (734) of logic circuit 700. 
FIG. 7 shows a possible power supply circuit 500 to provide all required 
voltages of the DSTMWI. Any form of input power could be used to supply 
DSTMWI power. For this example, a 12 v wall transformer 512 was used. 
Resistor 502 and zener diode 504 perform the task of voltage regulation to 
a level below wall transformer 512 output voltage. This removes any 
possible ripple. Resistors 506 and 508 form a voltage divider of half of 
the VCC voltage. Op-amp 510 provides a high current buffer for the 1/2 VCC 
which is used as a reference in various portions of the DSTMWI circuitry 
as previously described. 
FIGS. 8, 9A, 9B and 10 show the circuitry described above in an, enclosure. 
A typical embodiment of the combination of the enclosure and circuitry is 
illustrated in FIG. 9A. Additional embodiments are shown in FIGS. 9B, 10 
and 11. 
FIG. 8 shows the message waiting indicator unit in a typical connection set 
up for installation to a telephone line. FIG. 9A shows the unit having the 
capability for indication of different types of messages stored with the 
front enclosure 76 labeled with predetermined locations to identify the 
lamp 42 corresponding to a particular type of message stored. The visual 
indicator could also be different colored lamps. FIG. 9B shows the unit 
with its front enclosure 76 and back enclosure 74 which houses the 
circuitry 72, The unit connects to the tip and ring line-in through the 
telephone modular jacks 56. The visual indicator 42 sits within the 
housing illuminating the entire front enclosure. FIG. 10 further 
illustrates the stutter disable switch 1200 which allows switching between 
having notification from the FSK signal, the audible signal or both types 
of signals together. An audible indicator 44 is also shown sitting inside 
the housing. FIG. 11 shows an embodiment where the Caller ID viewing 
screen 78 is combined with the DSTMWI device previously described. 
The circuitry housed in the enclosure, as previously described, connects a 
standard tip and ring line to a telephone switch via the telephone modular 
jacks. The asynchronous FSK signal and/or an audible tone when sent via 
the telephone line to the message waiting circuitry triggers the 
notification devices of the unit. FIGS. 9A, 9B and 10 show the preferred 
equipment with the visual indicator(s) 42. Select switch 1200 allows the 
user to switch between FSK signaling only, audible tone detection only, or 
the combination of both used together. 
The message waiting indicator unit can be used to indicate the presence of 
different types of stored messages as shown in FIG. 9A. As previously 
described, connecting the unit to the telephone line via the telephone 
modular jack allows a designated signal as provided by the telephone 
switch to trigger the lamps 42 housed in the enclosure. The user will know 
the type of message, such as voice mail, E-mail, etc., that has been 
stored and is awaiting retrieval. Any combination of the lamps can be 
triggered on or off dependent upon the signal received. Multi-colored 
lamps or different colored lamps can also be used to identify the type of 
message stored. 
A combination Caller ID and dual signal triggered message waiting indicator 
is embodied in FIG. 11. A user of Caller ID service and Voice Mail 
services can use the same unit to receives the calling party's phone 
number and message waiting notification through audible tone detection.