U.S. patent number 3,674,936 [Application Number 05/014,771] was granted by the patent office on 1972-07-04 for voice conference system.
This patent grant is currently assigned to Burroughs Corporation. Invention is credited to Fred G. Wolfe.
United States Patent |
3,674,936 |
Wolfe |
July 4, 1972 |
**Please see images for:
( Certificate of Correction ) ** |
VOICE CONFERENCE SYSTEM
Abstract
The present application discloses a voice conference system
which may be utilized to provide virtual cut-through (VCT) service
when used in conjunction with a modular data processor in a store
and forward message switching system. The virtual cut-through
service so provided allows the transmission of continuous traffic
as well as digital voice communications. This feature coupled with
other novel characteristics of the system make it possible to
implement an extremely effective secure voice conference
service.
Inventors: |
Wolfe; Fred G. (Malvern,
PA) |
Assignee: |
Burroughs Corporation (Detroit,
MI)
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Family
ID: |
21767629 |
Appl.
No.: |
05/014,771 |
Filed: |
February 26, 1970 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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625067 |
Mar 22, 1967 |
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Current U.S.
Class: |
380/257;
379/202.01; 713/153 |
Current CPC
Class: |
H04L
12/54 (20130101) |
Current International
Class: |
H04L
12/54 (20060101); H04m 003/16 () |
Field of
Search: |
;179/1.5,1,1.5R,1CN |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Borchelt; Benjamin A.
Assistant Examiner: Birmiel; H. A.
Parent Case Text
CROSS REFERENCE TO RELATED U.S. PATENT
This application is a continuation of an earlier application filed
Mar. 22, 1967, Ser. No. 625,067 and now abandoned.
Claims
I claim:
1. A secure voice conference system comprising a switching center
including a plurality of incoming channels, a plurality of outgoing
channels, a plurality of functional modules connected therebetween
for transferring all data received by said incoming channels
directly to the proper outgoing channels without inspection of the
information contained in said received data, at least one of said
plurality of functional modules being a computing module and
including means for selectively activating the one of said incoming
channels having the highest precedence of a predetermined priority,
a plurality of subscriber sets, each having an enciphering means, a
deciphering means, a digital to voice conversion means and a voice
to digital conversion means adapted to receive audio signals and
couple its corresponding digital output signals to said enciphering
means for entry via one of said incoming channels to said switching
center, said digital to voice conversion means similarly adapted to
provide audio output signals upon receipt of corresponding digital
signals from said deciphering means for exit via one of said
outgoing channels from said switching center.
2. The system as set forth in claim 1 wherein each of said
subscriber sets includes means for interrupting said received audio
input signals and inserting a data word into the incoming stream of
audio signals at an interrupting period and rate such as to be
substantially harmless to the voice quality of the audio
signals.
3. The system as set forth in claim 2 wherein further means are
included for inserting into said data word a synchronizing marker
code to identify said information as a data word.
4. The system as set forth in claim 3 including further means in
each of said subscriber sets for inserting a priority cut-in binary
signal into said data word.
5. The system as set forth in claim 4 wherein each of said
subscriber sets also includes means for inserting a plurality of
talk request signals into said data word.
6. The system as set forth in claim 5 wherein each of said
subscriber sets further includes means for inserting into said data
word a plurality of conferee-present signals.
Description
The content of the related patent entitled "A Store and Forward
Message Switching System" by J.T. Lynch et al., U.S. Pat. No.
3,302,182, assigned to the present assignee, is to be included as
part of this disclosure, since it is in such a system that the
present invention will find a contemplated use.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to the transmission and reception of
continuous message traffic using a modular data processor as an
automatic secure message switching center. In addition, the present
invention discloses a means of providing the transmission of
continuous traffic as well as digital voice communications.
For many applications, it is desirable to provide the equivalent of
circuit-switching service in a message-switching center. One of
these applications is the transmission of continuous traffic or
very long messages; another, the transmission of voice
communications.
2. Description of the Prior Art
Previous switching centers have been capable of continuous traffic
or very long messages. However, in most cases, these systems
required continuous supervision of the traffic during these long
periods of transmission.
Another disadvantage of previous systems was that traffic did not
arrive in the exact order in which it was transmitted, without
interspersed messages from other sources.
In addition, because the same system components had to act upon
each incoming message, and further because these components
presented a fixed interface to all incoming messages, the use of
special codes in a message or the requirement by a message of a
special procedure was usually prohibited, since they were normally
incompatible with the fixed switching center requirements and hence
were not permitted.
Further, in those systems where voice communication was possible
the element of immediacy ideally required was not always
preserved.
BRIEF SUMMARY OF THE INVENTION
A system is provided for giving a modular data processinG system
the facility for providing virtual cut-through (VCT) service which
allows the transmission of continuous traffic as well as digital
voice communications. The term Virtual Cut-Through refers to the
ability of the system to receive the message and pass it through
the system for transmission practically simultaneously. That is, it
is accomplished as if the incoming circuit were actually switched
to the outgoing circuit as is done in a circuit switching system.
For example, in a telephone switching exchange the incoming call
circuit is physically switched to the selected outgoing lines. This
of course, would be actual cut through. In the present system this
is accomplished without circuit switching. Rather it is
accomplished by providing a path through the system between input
and output lines virtually directly. It is done without any
inspection of the incoming data whatsoever. This lack of inspection
of the incoming data simulates still closer, the operation in a
circuit switching system.
In the related U.S. Pat. No. 3,302,182, issued to the present
assignee, entitled "A Store and Forward Message Switching System
Utilizing a Modular Data Processing," By John T. Lynch and Fred G.
Wolff, a rather different concept is described. As it's title
implies, the incoming messages are are received, stored and later
forwarded out of the system. In the present system this store and
forward feature is bypassed to accomplish a virtual cut-through the
system by the message. Although a modular system is shown and
described, however, it is not a specific requirement for the
operation or practice of the presently proposed system. This, of
course, does not means that a data processing system is not
necessary, it merely means that a modular system is not required.
In a non-modular system, the conference is set up merely by
connecting the conferees to the input and output buffer means of
the data processing system. The advantages of using a modular
system for a store and forward message switching system is set
forth in the related application of Lynch et al. previously cited.
However, as noted therein, switching centers are possible using
data processing systems which are not modular. Thus, any switching
center may utilize the present scheme provided it is one in which
incoming and outgoing data are buffered before and after
processing. Further, although a Cryptographic Module (CPM) is
illustrated in the present embodiment, such a specific module is
not required. In the absence of the cryptographic module secure
traffic can be handled as described for unprotected traffic by the
use of conventional cryptographic equipment. In the present system
the virtual cut-through is accomplished by transferring all
incoming data directly to the proper outgoing channel(s) without
inspection of the data. Where protected channels are used this
transfer is done after deciphering and before enciphering. Thus,
different cryptographic techniques can be used on different
channels.
A plurality of the individual modules from a Modular Data
Processing system such as have been previously described in the
U.S. Pat. No. 3,302,182 are utilized in a unique configuration.
Thus a plurality of Data Buffer Modules (DBM) are utilized in
conjunction with a plurality of Data Demand Modules (DDM) to
provide a normal unprotected virtual cut-through path of
communications through a plurality of Memory Modules. (MM)
When a normal protected (secured) virtual cut-through path is
needed, an additional plurality of Cryptographic Modules together
with a plurality of Memory Modules used in association with a
Computer Module (CM) are required.
Among the advantages of this configuration are:
1. The switching center is relieved of continuous supervision of
traffic during long transmission periods;
2. Traffic arrives in the exact order in which it was transmitted,
without interspersed messages from other sources;
3. Special codes and procedures, not compatible with normal
switching center requirements, are permissible;
4. Generation of headers, etc., is not necessary;
5. The element of immediacy is preserved (for voice
communication).
BRIEF DESCRIPTION OF THE DRAWINGS
These and other features will become increasingly apparent when the
following specification is considered in conjunction with the
accompanying drawings. In the drawings:
FIG. 1 illustrates a block diagram showing the data flow for
Virtual Cut-Through (VCT) over both protected and unprotected
channels;
FIG. 2 shows an improved subscriber set configuration in a
suggested embodiment;
FIG. 3 provides a digital coding scheme for use with the present
system;
FIG. 4 illustrates a 48 bit data word showing the various signals
and the framing information.
In a message switching center, it is not practical (nor desirable)
actually to use circuit-switching techniques for the purpose of
connecting the input message lines to the output message lines.
Virtual cut-through can, however, be effected by transferring all
incoming data directly to the proper outgoing channel(s), without
inspection of the data. Where protected channels are used, this
transfer is done after deciphering and before enciphering (in clear
text). Thus, different cryptographic techniques can be used in
different links. A Cryptographic Processor Module may be used just
as in normal message-switching service. FIG. 1 illustrates the data
flow for Virtual Cut-Through (VCT) over both protected and
unprotected channels.
Once a VCT connection has been acquired, any kind of data,
including digital voice, can be transmitted. Present secure voice
transmission methods do not allow the superposition of two or more
voices. Thus it is necessary to permit only one conferee to talk at
a time. The controls that would be required for Secure Voice
Conference Service are normally difficult to implement, partly
because of their complexity. However, with a switching center, such
as that disclosed in U.S. Pat. No. 3,302,182 available, the
necessary control facility can be easily programmed into the
switching center's processor. To prevent superposition of voices, a
simple priority scheme is used, each participant automatically
excluding those "below" him while he is talking. The assignment of
conference precedence is made by the originator in the sequencing
of routing indicators when setting up the call or by other
procedural methods.
FIG. 1 shows the flow of information in and out of the switching
center. Encrypted digital voice channels are independently received
via the Data Buffer and Data Demand Modules, deciphered, and stored
in memory. The Computer Module examines the various incoming
channels and selects the one channel which will be transmitted to
all conferees.
The actual methods of selection of the voice to be transmitted
depends on the type of voice-encoding device used by the conferees.
In its simplest form the incoming channel of highest
(predetermined) precedence showing audio activity is selected for
transmission. (A more complex scheme is also described below.) In
any event, the data stored in the section of memory assigned to the
selected channel is transferred to the appropriate memory section
for independent re-enciphering and transmission to all
conferees.
Any type of digital voice communication can be used provided, of
course, that communication channels of sufficient bandwidth are
available between each participant and the switching center. The
voice-to-digital and digital-to-voice converters of all
participants must be compatible; but cryptographic equipment used
by subscribers may be of any type provided corresponding equipment
is provided at the switching center. For example, if a
Cryptographic Processor Module is included in the system, it can be
shared by all links at the switching center provided their
respective signalling speeds are the same.
To illustrate the additional capabilities of an automated secure
message switching center when it is provided with a more
sophisticated secure voice conference service, an improved
subscriber set utilizing a digital coding scheme is shown in FIGS.
2,3 and 4. At regular intervals the digItal voice stream is
interrupted and a 48-bit data word inserted. This short
interruption is not harmful to the voice quality. The data word
contains a 15-bit sync marker code to identify it as a data word.
In order to preclude the accidental interpretation of voice as data
should this 15-bit sequence be generated by the voice equipment,
the voice-generated data stream is continuously monitored, and
should any sequence occur, one of its bits is arbitrarily inverted.
This again, is not harmful to the voice quality. The 16 bit is a
priority cut-in signal. Bits 17-32 are talk request signals for up
to 16 conferees, and bits 33-48 are used to indicate the presence
of the 16 conferees.
Data words sent by the subscriber to the switching center are
utilized as follows. The voice to be transmitted is selected on the
basis of bits 16 to 32. If bit positions 17 to 32 are assigned to
subscribers in the order of predetermined precedence, the highest
binary value (bit position 16 is considered high order; 32 low
order) indicates the proper selection.
The data word is sent by each subscriber to the switching center.
The data word to be sent by the switching center to each subscriber
is generated in the following manner. The first 15 bits are, of
course, the sync marker. Bits 16 through 32 are copied from the
corresponding bits of the selected incoming channel. Bits 33
through 48 of all input channels are superimposed to produce the
corresponding output bits.
At the subscriber set, the incoming data word is used to indicate
visually those conferees present (bits 33 to 48), as well as the
individual presently speaking (bits 17 to 32).
Some of the unused combinations of data bits are assigned to
control functions, such as initiation and termination of calls.
Such unused data bits are those bits available to each subscriber
after his identification and speaking bits have been decided. Thus,
each subscriber requires only one of the 16 bits (33 to 48) for
indicating that he is present. Similarly, he requires only one bit
(of bits 17 - 32) to shown that he is presently speaking. The
remaining bits are available for other purposes.
Referring in particular to FIG. 1, there is illustrated in block
form the subscriber set 1-10. In this set there is included a voice
to digital converter 1-12, which receives the voice of the
particular conferee and converts it to a corresponding binary
digital representation. This digitally represented voice signal is
then coupled to the enciphering means 1-18, where it is encoded in
a predetermined manner. From there it is connected to the modular
processing system as an input line to the Data Buffer Module 1-22.
A number of other input information lines are also shown entering
the Data Buffer Module 1-22. Such lines may be assumed to be
connecting other subscriber sets similar to the set 1-10 to the
modular processing system.
The Data Buffer Module may be of the type disclosed and described
in the previously noted U.S. Pat. No. 3,302,182.
As its name implies, the enciphered information data is buffered
into the system by this module. Next, the Data Demand Module 1-24
scans the respective lines of the Buffer Module 1-22 and transfers
the selected information into the Memory Module 1-26.
From the stored contents of the Memory Module, the information may
take one of two paths dependent upon whether the information is
protected or unprotected. In this context, the words protected and
unprotected mean secured and unsecured respectively. Thus
classified messages would travel the protected or secured path
while unclassified information would be passed along the
unprotected or unsecured path.
In the case of a normal unprotected message, the virtual
cut-through path would be directly to the Memory Module 1-38, from
which it would pass through the Data Demand Module 1-40 and the
Data Buffer Module 1-42 to information output lines. In the
illustrated version, one set of output lines would be connected to
the Digital to Voice Converter 1-14 for transfer to the
Conferee.
A somewhat longer path is used for a protected message. In this
case, the protected message leaves the Memory Module 1-26 and
travels to the Cryptographic Module 1-28.
Although this path is shown as a direct line between the Memory
Module and the Cryptographic Module, it should be noted that this
is merely done for the sake of simplicity. Actually, the path is
through the Data Demand Module 1-24 and this is noted on the
drawing as via DDM.
From the Cryptographic Module 1-28, the protected path again
travels via the Data Demand Module 1-24 prior to the storage of the
protected message in clear text in the Memory Module 1-30. The
protected message was, of course, deciphered in the Cryptographic
Module prior to its transfer to the Memory Module 1-30.
From the Memory Module, the path of a normal protected virtual
cut-through message travels to the Memory Module 1-34 for ultimate
transfer out of the system. The protected message to be so
transferred is selected by the Computer Module 1-32. This selection
is based upon the degree of precedence and the Computer module 1-32
selects the active channel of the highest precedence in the Memory
Module 1-34 to accomodate the transfer.
The clear text of the message of the selected channel passes into
the Cryptographic Module 1-36. Here again this transfer is via a
Data Demand Modules 1-40. The Cryptographic Module 1-38 enciphers
the clear text of the message and then transfers it to the Memory
Module 1-38 again via the Data Demand Module 1-40.
From the Memory Module 1-38 the path of a normal protected virtual
cut-through is the same as the previously described path of a
normal unprotected VCT. Thus the message passes to the subscriber
set 1-10 and hence to the conferee.
In FIG. 2, a suggested embodiment of the subscriber is illustrated.
For example, the conferee selects a plurality of individuals upon
the pushbuttons of his conference selection means 2-16 and/or via
the telephone-like dial 2-18, or similar signaling means. These are
the particular parties whose presence he desires at the conference.
Those persons at the conference are noted by the "in conference"
lights 2-12, while the person speaking at the moment is noted by
the illumination of a "now speaking" light 2-10. In addition a set
of various predetermined conference groups are available to the
speaker by the repertoire selection means 2-20.
Finally, the "push-to-talk" means 2-22 provides its noted function
as does the "priority cut-in" means 2-14. It might be noted that
the conference initiator can decide the individual priorities of
the various conferees.
In FIG. 3, there is shown the digitally represented waveforms of a
voice transmission. This is illustrated in the upper portion of the
figure. At regular intervals 3-10,3-12,3-14 in the transmission a
48-bit data word is inserted. This is represented in greater detail
in the lower portion of the figure wherein the data segments 3-16,
3-18, 3-20 of the transmission are shown inserted between the voice
segments 3-22 and 3-24. It has been previously mentioned that these
48-bit data insertions are sufficiently short as not to appreciably
affect the quality of the voice transmission.
Finally, FIG. 4 identifies the 48 bits of the data word. Bits 1-15
include the sync and framing information 4-10, bit 16 determines
the priority cut-in signal 4-12, bits 17 to 32 provide the
talk-request signal 4-14 and bits 33 to 48 indicate those present
by the present signal 4-16.
While there has been shown and described a particular embodiment of
the present invention, it is obvious that many modifications are
possible which are within the scope of the present concept. It is,
therefore, the applicant's intention to be bound only by the scope
of the following claims.
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