Subscriber unit which is responsive to annunciation messages

A radio subscriber communication unit maintains an annunciation memory which stores a repertoire of annunciations. When the subscriber unit receives annunciation data messages from a communication network, a particular one of the annunciations is selected and presented to the user of the subscriber unit. An audible segment of the annunciation is passed through a vocoder, amplified, and routed to a speaker for presentation to the user. When annunciations are repeated, a second message may be received to instruct subscriber unit to cease presenting an annunciation.

TECHNICAL FIELD OF THE INVENTION 
The present invention relates generally to communication networks that 
provide communication services for subscribers. More specifically, the 
present invention relates to the presentation of signalling and other 
information to a user of a subscriber communication unit. 
BACKGROUND OF THE INVENTION 
Subscriber communication units, including telephone instruments and other 
telephonic devices, cellular radiotelephones, mobile radios, and the like, 
often link a human operator or user with a communication network. The user 
may converse with others through the communication network. These 
subscriber units use various techniques for presenting information to 
users concerning the state of communication services or of the subscriber 
unit. For example, dial tones, ringing sounds, and busy signals are common 
audible annunciations that a subscriber unit presents to a user. Many 
subscriber units include indicator lights and displays to visually present 
annunciations describing dialled telephone numbers, active telephone lines 
in multiple line units, service conditions, and the like. 
Various signalling practices that have evolved from land-line communication 
systems are undesirable in connection with the presentation of 
annunciations in radio communication systems. For example, many linguistic 
or voice messages and audio sounds that are presented to a user through a 
subscriber unit are generated at a central switching office and 
transmitted to the subscriber unit for presentation to the user. Such 
messages and sounds consume a greater amount of the electromagnetic 
spectrum than may be justified for the quantum of information being 
conveyed. As more and more calls are communicated using a finite amount of 
the electromagnetic spectrum, the need to utilize the spectrum as 
efficiently as possible becomes acute. 
Moreover, conventional signalling practices do not adequately account for 
the fact that some of the people using a communication system speak 
foreign languages. Subscribers who roam in foreign-speaking areas often 
have difficulty understanding voice messages which are not voiced in a 
language with which they are conversant. This problem becomes especially 
troublesome in communication systems which span areas of coverage within 
which many languages are spoken. And, the troublesome nature of this 
problem is multiplied for radio communication systems which tend to have 
numerous diverse system states about which explanations need to be 
communicated to subscribers. 
Still further, conventional practices are poorly suited for various 
signalling annunciations which must be presented to users of digital 
communication systems. In digital communication systems, voice data are 
often encoded and/or compressed for transmission through a communication 
network. When a circuit between two parties has been established and a 
call is ongoing, patching into the call to deliver additional signalling 
information, such as a call waiting "click", is a complicated matter due 
to the encoding. One possible technique for patching into an ongoing call 
might be to route the ongoing call to a central location, decode the 
digitized call data, mix the decoded call data with signalling data, 
re-encode the mixed call and signalling data, and route the re-encoded 
mixture of call and signalling data to the call's destination. However, 
this technique is highly undesirable due to the significant additional 
communication resources needed. The allocation of significant additional 
resources to convey simple signalling information can waste scarce 
electromagnetic spectrum and other network resources. 
SUMMARY OF THE INVENTION 
Accordingly, it is an advantage of the present invention that an improved 
subscriber unit and method of operating a subscriber unit is provided. 
Another advantage of the present invention is that a subscriber unit is 
provided for which only an insignificant amount of spectrum need be 
allocated for conveying signalling information. 
Another advantage of the present invention is that a subscriber unit is 
provided which permits a user to roam in areas where foreign languages are 
spoken and still receive voice messages in a preferred language. 
Yet another advantage is that a subscriber unit is provided which 
accommodates the interleaving of signalling messages and encoded audio 
data without requiring the allocation of additional channels. 
The above and other advantages of the present invention are carried out in 
one form by a method of operating a subscriber communication unit that 
communicates with a communication network, has memory for storing data, 
and has a user interface through which a user of the subscriber unit 
perceives annunciations. The method calls for storing annunciation data in 
the memory. The annunciation data serves as a repertoire of annunciations. 
Data transmitted from the communication network is monitored to detect an 
annunciation data message. Annunciation data messages instruct the 
subscriber unit to perform an annunciation, and annunciation data messages 
convey identity data which specify one of the annunciations. When an 
annunciation data message is detected, a portion of the annunciation data 
is selected. The selected portion of annunciation data is chosen in 
response to the identity data. In addition, the user interface is 
controlled with the selected portion of the annunciation data to present 
the specified annunciation to the user.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
FIG. 1 illustrates a world-wide, satellite-based communication network 10 
with which the preferred embodiments of the present invention may be 
practiced. Network 10 includes a constellation of switching nodes 12 that 
are dispersed around the earth. In the preferred embodiments, nodes 12 are 
orbiting satellites. Network 10 preferably includes a sufficient number of 
satellites 12 so that communication with one of the satellites 12 may take 
place from substantially any point on the surface of the earth through the 
use of a subscriber unit 14. 
Network 10 may accommodate any number, potentially in the millions, of 
subscriber units 14. In the preferred embodiments of the present 
invention, subscriber units 14 communicate with nearby satellites 12 via 
subscriber links 16. Links 16 encompass a limited portion of the 
electromagnetic spectrum that is divided into numerous channels. As a 
minimum, a satellite 12 continuously transmits over one or more broadcast 
channels 18. Subscriber units 14 synchronize to broadcast channels 18 and 
monitor broadcast channels 18 to detect data messages which may be 
addressed to them. Subscriber units 14 may transmit messages to satellites 
12 over one or more random access channels 20. Broadcast channels 18 and 
random access channels 20 are not dedicated to any one subscriber unit 14 
but are shared by all subscriber units 14 currently within view of a 
satellite 12. 
On the other hand, traffic channels 22 are two-way channels that are 
assigned to particular subscriber units 14 by satellites 12 from time to 
time. In the preferred embodiments of the present invention, a digital 
format is used to communicate data over channels 18-22, and traffic 
channels 22 support real-time communications. At least one traffic channel 
22 is assigned for each call, and each traffic channel 22 has sufficient 
bandwidth to support, as a minimum, a two-way voice conversation. To 
support real-time communications, a time division multiple access (TDMA) 
scheme is used to divide time into frames, preferably in the 60-90 
millisecond range. Particular channels 22 are assigned particular transmit 
and receive timeslots, preferably having durations in the 3-10 millisecond 
range, within each frame. Analog audio signals are digitized so that an 
entire frame's signal is transmitted or received in a single short high 
speed burst during an allotted timeslot. Preferably, each satellite 12 
supports up to a thousand or more traffic channels 22 so that each 
satellite 12 can simultaneously service a like number of independent 
calls. 
Satellites 12 communicate with other nearby satellites 12 through cross 
links 24. Thus, a communication from a subscriber unit 14 located at any 
point on or near the surface of the earth may be routed through the 
constellation of satellites 12 to within range of substantially any other 
point on the surface of the earth. A communication may be routed down to a 
subscriber unit 14 on or near the surface of the earth from a satellite 12 
using a subscriber link 16. Alternatively, a communication may be routed 
down to or up from any of many central switching offices (CSOs) 26, of 
which FIG. 1 shows only two, through earth links 28. CSOs 26 preferably 
couple to local public switched telecommunications networks (PSTNs) 29. 
Communications from network 10 may be routed through PSTNs 29 to any 
telephonic instrument or other device which also couples to a PSTN 
throughout the world. CSOs 26 are preferably distributed over the surface 
of the earth in accordance with geo-political boundaries. In the preferred 
embodiments, each satellite 12 may communicate with up to four CSOs 26 and 
over a thousand subscriber units 14 at any given instant. 
Accordingly, network 10 may establish a bidirectional communication circuit 
or two unidirectional circuits through the constellation of satellites 12 
between any two subscriber units 14, between any subscriber unit 14 and 
any CSO 26, between any two CSOs 26, or between any subscriber unit 14 and 
any telephonic device. Any two ends of a given connection may be located 
in areas of the world where different languages are spoken, and users of 
subscriber units 14 may carry their subscriber units 14 with them for use 
in any region of the world where any language may be spoken. 
As discussed above, communications in the preferred embodiments are 
configured into a digital format. FIG. 2 shows a block diagram of an 
exemplary data packet 30 that may be used to transport a communication to 
a subscriber unit 14 (see FIG. 1). Packet 30 includes a header 32, which 
carries data identifying a type characterization to be associated with 
packet 30, a length to be associated with packet 30, and any other 
information conventionally included in data packet headers. The type 
characterization may indicate whether the packet 30 exclusively conveys 
system control messages or whether it conveys subscriber traffic. A 
routing code 34 is included to instruct network 10 (see FIG. 1) where to 
deliver packet 30. 
A subscriber ID 36 represents a code that uniquely identifies a subscriber 
unit 14 and that is known to the identified subscriber unit 14 and any 
satellite 12 (see FIG. 1) providing a traffic channel 22 (see FIG. 1) to a 
subscriber unit 14. A subscriber unit 14 monitors subscriber IDs 36 of 
packets 30 transmitted over a broadcast channel 18 (see FIG. 1) to 
determine if the packets 30 are intended for it. A satellite 12 uses 
subscriber IDs 36 of packets 30 that carry subscriber traffic to route 
such packets 30 to the traffic channels 22 assigned to the identified 
subscriber units 14. 
Header 32, routing code 34, and subscriber ID 36 represent overhead data 
which serve to get packet 30 to its destination. At the packet's 
destination, payload data 38 are consumed. In other words, the purpose of 
sending packet 30 to a destination is typically to deliver payload data 
38, not header 32, routing code 34, or subscriber ID 36. Payload data 38 
includes either system control data 40 or system control data 40 together 
with subscriber traffic 42. System control data 40 are commands or 
messages which are interpreted and acted upon by subscriber units 14. 
These commands are typically very short. When system control data 40 are 
delivered over a broadcast channel 18, subscriber traffic 42 is omitted, 
and the resulting packet 30 is very short so that as many messages as 
possible may be broadcast over the broadcast channel 18. Subscriber 
traffic 42 represents all subscriber data transported in the course of a 
call. When a packet 30 is delivered over a traffic channel 22, a 
significant amount of subscriber traffic is appended. As discussed above, 
a digitized version of an entire frame of conversational audio is conveyed 
by subscriber traffic 42. 
Compared to the size of subscriber traffic 42, the length of system control 
data 40 is insignificant. Thus, system control data 40 may be delivered to 
a subscriber unit 14 along with subscriber traffic 42 while a call is 
ongoing. Examples of system control messages which may be delivered with 
subscriber traffic 42 via a traffic channel 22 include messages which 
inform a subscriber unit 14 that the other party to a call has "hung-up," 
that another call is waiting for the subscriber unit 14, and any number of 
annunciation data messages which result in a voice message or other form 
of annunciation being presented to the user of subscriber unit 14. An 
annunciation which may be presented to a user while a call is ongoing may, 
for example, warn a user when communication services are soon expected to 
become unavailable or when any other service condition warrants. 
FIG. 3 shows a block diagram of a subscriber unit 14 configured in 
accordance with the preferred embodiments of the present invention. 
Subscriber unit 14 may be a portable or mobile, battery-operated, radio 
device. Thus, subscriber unit 14 includes a battery 44 which supplies 
electrical energization for all components within subscriber unit 14. For 
clarity, FIG. 3 omits these power connections. 
A controller 46 may be provided by one or more microprocessor circuits. 
Controller 46 has a data input which couples to battery 44 so that battery 
voltage may be monitored. Controller 46 additionally couples to a receiver 
and data buffer 48, a transmitter and data buffer 50, a switch or 
multiplexer 52, a general memory 54, a user interface 56, and an 
address/data bus 58 for an annunciation memory 60. Annunciation memory 60, 
general memory 54, and data buffers associated with receiver 48 and 
transmitter 50 are preferably provided by semiconductor memory circuits. 
Those skilled in the art will appreciate that such circuits need not be 
partitioned in any particular way. However, in one preferred embodiment, 
annunciation memory 60 represents a permanent or removable memory which 
may be personalized for a particular user and installed or programmed at 
the time the user acquires subscriber unit 14 or prior to use of 
subscriber unit 14. 
Receiver 48 receives incoming RF data from network 10 (see FIG. 1) and 
places such data in its internal data buffer. Controller 46 tunes receiver 
48 to specified channels and accesses data in the buffer of receiver 48. 
System control messages are retrieved and processed by controller 46. 
Receiver 48 additionally couples to a first input port of switch 52, and a 
data output of annunciation memory 60 couples to a second input port of 
switch 52. An output of switch 52 couples to a vocoder 62. Hence, 
controller 46 determines whether subscriber traffic is routed from 
receiver 48 through switch 52 to vocoder 62 or whether annunciation data 
is routed from annunciation memory 60 through switch 52 to vocoder 62. 
Vocoder 62 receives digital data from switch 52 and translates such data 
into an analog audio signal. Preferably, vocoder 62 is configured to 
expand a stream of correspondingly encoded and compressed digital data 
supplied at a rate of 2400-4800 baud into conversational quality audio. An 
analog output of vocoder 62 couples to an audio amplifier 64, and an 
output of amplifier 64 couples to a speaker 66. Audio, whether 
annunciations from annunciation memory 60 or subscriber traffic from 
receiver 48, is presented to a user of subscriber unit 14 through speaker 
66. 
A microphone 68 couples to an input of a microphone pre-amplifier 70, and 
an output of pre-amplifier 70 couples to an analog input of vocoder 62. 
Vocoder 62 digitizes, encodes, and compacts audio obtained from microphone 
68 into a digital form compatible with network 10. Vocoder 62 also has an 
output for outgoing digital data that couples to an input of transmitter 
50 so that the encoded data may be placed in a buffer thereof. Transmitter 
50 modulates the outgoing data to RF for transmission to network 10. 
Speaker 66 and microphone 68, discussed above, are components of user 
interface 56 because they present information to and collect information 
from, respectively, a user of subscriber unit 14. User interface 56 
additionally includes a display 72, a switch bank 74, and a data port 76, 
each of which couples to controller 46. Display 72 visually presents 
annunciations to the user, and switch bank 74 receives inputs from the 
user. In particular, switch bank 74 includes a conventional keypad along 
with other switches, such as a power control key, a send key, a hookswitch 
or its equivalent, and any other keys conventionally used in 
telecommunication equipment. The hookswitch or its equivalent is 
manipulated by a user to indicate the answering or the termination of a 
call. Those skilled in the art will appreciate that subscriber unit 14 
need not be limited to conveying audio information, but may convey digital 
data to and from network 10 as well. Data port 76 is used in transferring 
such digital data to and from subscriber unit 14. 
General memory 54 includes data which serve as instructions to controller 
46 and which, when executed by controller 46 cause subscriber unit 14 to 
carry out procedures which are discussed below in connection with FIGS. 
4-7. In addition, memory 54 includes variables, tables, and databases that 
are manipulated due to the operation of subscriber unit 14. 
FIG. 4 shows a flow chart of a Start procedure 78, which is performed when 
subscriber unit 14 is energized or when subscriber unit 14 loses 
subscriber link 16 (see FIG. 1). Start procedure 78 performs a task 80 to 
synchronize to or capture a broadcast channel 18 (see FIG. 1) transmitted 
by an overhead satellite 12 (see FIG. 1). A broadcast channel 18 may be 
considered captured when subscriber unit 14 can read valid data carried by 
the broadcast channel 18. Due to variations in Doppler and propagation 
time of broadcast channels 18, controller 46 (see FIG. 3) may need to 
instruct receiver 48 (see FIG. 3) to search for some period of time before 
it can lock onto a broadcast channel 18. In addition, receiver 48 may need 
to discriminate between multiple broadcast channels 18 transmitted by one 
or more satellites 12. Accordingly, after an appropriate period of time, a 
query task 82 determines whether a broadcast channel 18 has been captured. 
A subscriber unit 14 may fail to capture a broadcast channel 18 for any one 
of several reasons. For example, a subscriber unit 14 may be located 
underground, within a building, or near some interfering structure. When 
task 82 determines that subscriber unit 14 has failed to capture a 
broadcast channel 18, program control proceeds to a Present Annunciation 
procedure 84, which is detailed below in connection with FIG. 7. 
Generally speaking, Present Annunciation procedure 84 causes subscriber 
unit 14 to present an appropriate annunciation to the user of subscriber 
unit 14. The annunciation may be a voice message, a distinctive audible 
sound, a visual display, or the activation of an indicator light. In this 
situation, the annunciation will communicate to the user that 
communication services through network 10 are not currently available. An 
audible voice message may go on to explain that movement away from 
interfering structures may help in obtaining communication services. 
Accordingly, subscriber unit 14 detects a condition, such as the inability 
to contact network 10, that warrants the presentation of information 
describing the condition to the user. Then, subscriber unit 14 presents an 
appropriate annunciation to the user. 
When task 82 determines that a broadcast channel 18 has been captured, a 
task 86 causes subscriber unit 14 to log-on to network 10. The log-on 
process is accomplished by causing subscriber unit 14 to transmit a log-on 
message via a random access channel 20 (see FIG. 1). Network 10, and 
particularly a nearby CSO 26 thereof, interprets the log-on message as a 
request for registering the identified subscriber unit 14 to obtain 
communication services. After subscriber unit 14 logs on to network 10, a 
Background procedure 88 is enabled, as indicated by a dotted line, and 
process control concurrently proceeds to a Standby procedure 90. 
Background procedure 88 is discussed below in connection with FIG. 5, and 
Standby procedure 90 is discussed below in connection with FIG. 6. 
FIG. 5 shows a flow chart of tasks performed by subscriber unit 14 during 
Background procedure 88. Those skilled in the art will appreciate that 
Background procedure 88 runs continuously in a background mode even though 
other procedures, such as Present Annunciation procedure 84 and Standby 
procedure 90, may be concurrently active. In other words, regardless of 
other tasks subscriber unit 14 may be currently undertaking, a task 92 of 
Background procedure 88 is performed to monitor channels broadcast by 
network 10. A query task 94 evaluates this data to determine if a packet 
30 (see FIG. 2) is being directed to the subscriber unit 14. If a packet 
30 is being directed to subscriber unit 14, a task 96 saves the payload 38 
(see FIG. 2) from the packet 30 in a job queue created in memory 54 (see 
FIG. 3). Other foreground procedures, such as Standby procedure 90, will 
evaluate this job queue and treat the data received from the packet 30 as 
an instruction to take some action. 
After task 96 or when task 94 determines that no packet is addressed to the 
subscriber unit 14, a task 98 monitors user interlace 56 (see FIG. 3) for 
inputs. Next, a query task 100 determines if a user input is present. If a 
user input is present, a task 102 collects the input and saves the input 
in the above discussed job queue. Such user inputs may, for example, 
indicate that the user of subscriber unit 14 is dialling a phone number or 
is ready to send the number to network 14 to ring the called party. 
After task 102 or when task 100 fails to detect any user input, a task 104 
monitors battery level. If the battery is becoming seriously run down, a 
query task 106 activates Present Annunciation procedure 84. This time, 
Present Annunciation procedure 84 causes subscriber unit 14 to present an 
annunciation to the user which informs the user that the battery is low 
and that continued operation may be unreliable. The low battery level is 
another example of a condition detected by subscriber unit 14 that 
warrants the presentation of information describing the condition to the 
user. After completion of Present Annunciation procedure 84 and when task 
106 determines that battery level is within acceptable limits, program 
control returns to task 92, discussed above, and program control 
continuously remains in a loop which includes various ones of tasks 
92-106. 
FIG. 6 shows a flow chart of Standby procedure 90. Procedure 90 includes a 
query task 108 which detects whether an annunciation data message has been 
received from network 10. Task 108 may make its determination by 
evaluating data included in the job queue. When an annunciation data 
message is present, Present Annunciation procedure 84 is performed to 
present the annunciation indicated by the message to the user. Those 
skilled in the art will appreciate that, at this point, an entire 
annunciation data message has been received by subscriber unit 14. From 
the perspective of network 10, this communication with subscriber unit 14 
has ended, and network 10 may now be using its scarce resources in 
providing services to other subscriber units 14. Network 10 need not 
allocate its resources to this subscriber unit 14 until the annunciation 
has been completely presented to the user. Thus, network 10 has consumed 
only an insubstantial amount of its resources in delivering the 
annunciation data message to the subscriber unit 14. After procedure 84 
presents the indicated annunciation, program control returns to task 108. 
When task 108 fails to detect an annunciation data message, a query task 
110 determines whether a connect call request has been received. A connect 
call request may originate from network 10 when the subscriber unit 14 is 
the called party in an upcoming call. Thus, task 110 monitors the job 
queue to determine if a network system message has been received informing 
subscriber unit 14 of a request to set up a call. Alternatively, a connect 
call request may be made by the user of subscriber unit 14 when subscriber 
unit 14 is the calling party in an upcoming call. Task 110 also monitors 
the job queue to determine if a user input signalling a desire to send a 
dialled number has been detected from switch bank 74 of user interface 56 
(see FIG. 3). If no requests to connect a call are detected, program 
control returns to task 108, discussed above. 
On the other hand, if task 110 detects a request to connect a call, task 
112 is performed to complete the call setup process. The preferred 
embodiments of the present invention contemplate the use of conventional 
call setup processes known to those skilled in the art of telephony at 
task 112. For example, when subscriber unit 14 is the called party, a 
ringing signal is presented to the user, an event equivalent to 
"answering" is detected, the answering event is communicated to network 
10, and receiver 48 and transmitter 50 (see FIG. 3) are tuned to a traffic 
channel 22 assigned by network 10. If an answering event is not detected, 
signalling commands from network 10 indicate when the calling party "hangs 
up" so that ringing at the subscriber unit 14 may be terminated. 
When subscriber unit 14 is the calling party, the subscriber unit sends the 
called party's identifying number to network 10. System messages received 
back from network 10 during call setup inform the subscriber unit 14 of 
the progress of the call. A variety of "busy" messages may be sent to 
subscriber unit 14 when network 10 circuits are unavailable. Another busy 
message may be sent to subscriber unit 14 when the called party's line or 
the equivalent is currently in use. A ringing message may be sent to 
subscriber unit 14 when the called party's telephonic or radio device is 
ringing. In addition, a variety of other call progress messages may be 
sent to subscriber unit 14 during call setup so that subscriber unit 14 
knows that call setup is progressing. When the called party answers, a 
network message may communicate the identity of a traffic channel 22 to 
use in the upcoming call and subscriber unit 14 may then tune its receiver 
48 and transmitter 50 to this channel. 
As indicated in FIG. 6, network system messages received at subscriber unit 
14 during call setup activate Present Annunciation procedure 84. In one 
embodiment of the present invention, explicit annunciation data messages 
are received at subscriber unit 14. The explicit annunciation data 
messages are interpreted by subscriber unit 14 exclusively as commands to 
present annunciations to the user. Such explicit annunciation data 
messages include data that directly identify a particular annunciation to 
present to the user. In another embodiment of the present invention, 
implicit annunciation data messages are received at subscriber unit 14. 
Implicit annunciation data messages are interpreted by subscriber unit 14 
as commands to present annunciations to the user and possibly to perform 
other tasks. Subscriber unit 14 may need to translate or otherwise process 
data conveyed by implicit annunciation data messages in order to identify 
a particular specified annunciation. In either embodiment, data 
identifying a specified annunciation are conveyed with the system message. 
For example, when subscriber unit 14 receives a system message informing it 
of an incoming call, subscriber unit 14 may interpret such a message as an 
instruction to present a ringing signal annunciation to the user. When 
subscriber unit 14 receives a system message informing it of a busy 
condition, subscriber unit 14 may interpret such a message as an 
instruction to present a particular annunciation to the user. This 
annunciation may be a conventional "busy" sound when the called party's 
line is currently in use and may be a variety of different voice messages 
when circuits within network 10 are currently unavailable. A ringing 
feedback annunciation may be presented when network 10 informs a calling 
subscriber unit 14 that the called party is being rung. When network 10 
informs subscriber unit 14 that the called party has answered, subscriber 
unit 14 may interpret such a system message as an instruction to cease the 
ringing feedback annunciation. 
Those skilled in the art will appreciate that the precise content of 
various annunciations is not an important feature in the present 
invention. Moreover, those skilled in the art will appreciate that system 
resources are utilized more efficiently by communicating system messages 
which are interpreted by subscriber unit 14 as instructions to present 
internally stored annunciations to the user, rather than allocating system 
resources to establishing audio quality communication links so that audio 
annunciations may be transmitted from a central switching office to the 
subscriber units for presentation to users. 
After task 112 completes the call setup process, a task 114 essentially 
manages the ongoing, call. In other words, outgoing analog signals from 
microphone 68 (see FIG. 3) are translated into outgoing vocoded digital 
data and transmitted to network 10 via a traffic channel 22 assigned by 
network 10 for this call. Likewise, incoming digital vocoded data are 
received from network 10 over the traffic channel 22, decoded, translated 
into incoming analog audio signals, and presented to the user through 
speaker 66 (see FIG. 3). Of course, those skilled in the art will 
appreciate that in order to support real time communications, task 114 is 
enabled during Standby procedure 90 and performed continuously during a 
background mode of operation. In other words, subscriber unit 14 may 
undertake other tasks and procedures during the ongoing call, but 
subscriber unit 14 continues to perform task 114. 
One of the other tasks undertaken by subscriber unit 14 during an ongoing 
call is a query task 116. Query task 116 monitors the stream of packets 30 
(see FIG. 2) received over traffic channel 22 for the presence of a system 
control message 40 (see FIG. 2). In particular, task 116 detects the 
presence of an annunciation data message. When such a message is present, 
Present Annunciation procedure 84 is activated to present the annunciation 
indicated by the message to the user. When such messages are audible 
annunciations, controller 46 controls switch 52 to route data from 
annunciation memory 60 to vocoder 62. After completion of the message, 
controller 46 sets switch 52 to allow data from receiver 48 to flow to 
vocoder 62, and program control continues to process the ongoing call. 
Accordingly, annunciations, whether audible, visible, or both, may be 
presented to a user during an ongoing call through the inclusion of a 
relatively short system control message in one packet 30 from a stream of 
packets 30 that are being routed to subscriber unit 14. Examples of these 
annunciations may be call waiting annunciations or annunciations warning 
users of expected upcoming interruptions in communication services. 
A query task 118 is also performed during ongoing calls. Task 118 
determines whether the call has finished. The call may be finished when 
the user of subscriber unit 14 "hangs up." This event may be detected 
through the operation of Background procedure 88, discussed above, and the 
monitoring of data in the job queue. In addition, the call may finish when 
the opposing party hangs up. This situation is detected by monitoring 
packets 30 (see FIG. 2) for system control messages 40 (see FIG. 2) that 
signal call termination. So long as the call has not yet finished, 
subscriber unit 14 continues to manage the ongoing call, as indicated in 
FIG. 6 by looping back to task 114, discussed above. When the call is 
finished, a task 120 performs any processes needed to terminate the call, 
and program control then returns to task 108. 
FIG. 7 shows a flow chart of tasks performed by subscriber unit 14 during 
Present Annunciation procedure 84. Procedure 84 performs a task 122 to 
obtain the identity of an annunciation to be presented to the user. As 
discussed above, this identity may be explicitly or implicitly 
communicated to subscriber unit 14. After task 122, a task 124 uses the 
identity data to get performance parameters for the annunciation. For 
example, performance parameters may indicate whether to blink visual 
annunciations, whether to repeat audible annunciations, what conditions to 
use as a signal to terminate repetitions, and/or a list of separate small 
annunciations which are chained together to form a large annunciation. 
FIG. 8 shows a block diagram of an exemplary memory structure 126 which may 
be used by procedure 84 in presenting annunciations. Structure 126 
provides a repertoire of annunciations and is preferably maintained in 
annunciation memory 60 (see FIG. 2). As shown in FIG. 8, structure 126 is 
divided into discrete annunciation portions 128. Each annunciation portion 
128 may include a performance parameter segment 130 that provides the data 
obtained in task 124 (see FIG. 7). In addition, each annunciation portion 
128 may include a visual segment 132 and an audible segment 134. Visual 
segment 132 contains data that are presented visually at display 72 (see 
FIG. 3), and audible segment 134 contains data that are presented audibly 
at speaker 66 (see FIG. 3). An annunciation portion 128 may omit visual 
segment 132 when an annunciation is exclusively presented audibly or may 
omit audible segment 134 when an annunciation is exclusively presented 
visually. Of course, those skilled in the art will appreciate that data 
stored in audible segment 134 are encoded and compressed so that, when 
processed by vocoder 62 (see FIG. 3), meaningful audible sounds and 
language result. The meaningful audible sounds include non-verbal sounds, 
such as conventional telephonic ringing signals, busy signals, and dial 
tones. The audible sounds additionally include voice messages expressed in 
a selected language. 
In one embodiment of the present invention, memory structure 126 includes a 
language dimension so that each annunciation portion 128 is expressed in a 
variety of different languages 136. However, in a currently more preferred 
embodiment, a user selects a language within which he or she wishes to 
receive annunciations at the time of purchase, and structure 126 is 
programmed into subscriber unit 14 at that time to incorporate only that 
selected language. In this more preferred embodiment, only one language 
136 is included to conserve memory requirements of subscriber unit 14. 
With reference back to FIG. 7, after task 124 obtains the identified 
annunciation's performance parameters, an optional task 137 selects the 
language to use in presenting the annunciation. Task 137 is performed only 
when multiple languages 136 (see FIG. 8) are included in memory structure 
126 (see FIG. 8). The user may indicate a language selection via switch 
bank 74, and this selection may then be stored in a variable in memory 54 
(see FIG. 3). Of course, if only one language is included in memory 
structure 126 then task 137 may be omitted. 
After task 137, a query task 138 determines whether a visual segment 132 
(see FIG. 8) has been requested for this annunciation. This determination 
may be made by evaluating the performance parameters or by determining 
whether a visual segment 132 has been included in the selected 
annunciation portion 128 (see FIG. 8). If a visual segment 132 has been 
specified, a task 140 obtains the visual segment 132 from the identified 
annunciation portion 128 and programs display 72 (see FIG. 3) with the 
data from this segment. 
After task 140 and when task 138 determines that no visual segment 132 (see 
FIG. 8) has been specified for the identified annunciation, a query task 
142 determines whether an audible segment 134 (see FIG. 8) has been 
specified. If an audible segment 134 has not been specified, program 
control exits procedure 84 and returns to the calling procedure. 
When an audible segment has been specified, a task 146 selects the 
identified audible segment 134 (see FIG. 8) of the identified portion 128 
of memory structure 126 by appropriate control of address bus 58 (see FIG. 
3). This selected audible segment 134 is then routed to vocoder 62 through 
switch 52 (see FIG. 3) at an appropriate data rate. After task 146, a 
query task 148 determines whether the audible annunciation requires 
repeating. Non-verbal annunciations, such as ringing, feedback ringing 
during call origination, busy signals, and dial tones typically repeat a 
small segment of an annunciation until some external event occurs. 
However, nothing prevents voice messages and other annunciations from 
being repeated as well. When the annunciation is not repeated, program 
control exits procedure 84. Performance parameters 130 (see FIG. 8), 
obtained above in task 124, may be examined to determine whether 
repetitions are needed. 
When the annunciation being presented to the user by procedure 84 is a 
repeated annunciation, a query task 150 determines whether to terminate 
repetitions. Performance parameters 130 (see FIG. 8) obtained above in 
task 124 may specify upon which conditions to terminate repetitions. Such 
conditions may include the reception of a system control message which 
instructs that the annunciation be terminated. For example, when a 
subscriber unit 14 originates a call, a system message may instruct the 
subscriber unit 14 that the other party has answered the call. In this 
situation, subscriber unit 14 may terminate the feedback ringing 
annunciation. Alternatively, busy signals and dial tones may continue 
until a user hangs up, or the equivalent. When task 150 determines that 
repetitions need to continue, program control returns to task 146 to 
repeat the presentation of the annunciation to the user. When task 150 
determines that repetitions may terminate, program control exits procedure 
84 and returns to the calling procedure. 
In summary, the present invention provides an improved subscriber unit and 
method of operating a subscriber unit. Annunciations are presented to a 
user in response to the receipt of short system control messages. 
Consequently, only an insignificant amount of spectrum is used to perform 
subscriber unit annunciations. Moreover, annunciations are stored within a 
subscriber unit in a language that is selected by the user. Thus, a user 
may roam in areas where foreign languages are spoken and still receive 
voice messages in his or her preferred language. Furthermore, brief system 
control messages may be interleaved with digitized data packets that carry 
real time voice conversations. No additional system resources need be 
allocated to communicate signalling information to the subscriber unit 
while calls are ongoing. 
The present invention has been described above with reference to preferred 
embodiments. However, those skilled in the art will recognize that changes 
and modifications may be made in these preferred embodiments without 
departing from the scope of the present invention. For example, the 
network with which the subscriber unit communicates need not be a 
space-based network, but may be any communication system. Moreover, the 
vocoder described herein may be replaced with a voice synthesizer or other 
digital-to-audio/voice device. Furthermore, those skilled in the art will 
readily understand that a wide range in organization and structure of 
tasks and memory structures may be employed in constructing the present 
invention. These and other changes and modifications which are obvious to 
those skilled in the art are intended to be included within the scope of 
the present invention.