Scheduled internet protocol telephone instrument system

Details Scheduled internet protocol telephone instrument system Scheduled internet protocol telephone instrument system

2001-02-08

2003-04-29

Olms, Douglas (Department: 2661)

Multiplex communications

Pathfinding or routing

Combined circuit switching and packet switching

C370S443000, C370S498000, C379S088170

Reexamination Certificate

active

06556564

ABSTRACT:

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
N/A
BACKGROUND OF THE INVENTION
The present invention relates generally to telephone instruments, and more specifically to telephone instruments that are directly connected to a data LAN (Local Area Network).
As it is generally known, telephone systems for business use normally consist of a central switch or Private Branch exchange (PBX), illustrated by PBX
16
shown in
FIG. 2
, which connects to telephones throughout the business via a twisted pair wire
14
and
15
. An example of such a system configuration is depicted in FIG.
2
. In most cases the PBX
16
will use a single twisted pair cable
14
to connect with the telephone instrument
13
. During operation of the system shown in
FIG. 2
, the PBX
16
sends signals to and receives signals from the telephone instruments
10
and
13
via a frequency translated modem system.
Existing PBX systems typically use dedicated wiring, shown as multi-pair cables
15
in
FIG. 2
, connected to the PBX
16
. The multi-pair cables
15
are connected to punch-down blocks
12
. The punch-down blocks
12
are normally placed in a closet on the floor of the office building, near the telephone instruments
10
and
13
. The individual station cables
14
are also connected to the punch-down blocks
12
. The station cables
14
lead to the wall jacks
11
. The telephone instruments
10
and
13
are connected to the system via instrument cables
18
to the wall jack
11
. The telephones
10
and
13
are powered via a DC current that is carried by the same pair as that used for signaling. Telephone calls are made outside the premises via a Wide Area Network (WAN) link
17
connected to the PBX unit
16
. The WAN link
17
is often a multi-channel circuit, such as what are commonly referred to as “T1” or “PRI” links.
The typical existing PBX system requires dedicated wiring. It does not share wiring with the data LAN that is common in most businesses. Thus, two wiring networks are normally required within an office building, one for data and one for telephones.
Recently, a technique for creating a “virtual” PBX has been employed that is referred to as a “LAN-PBX.” In this technique, the telephone instrument uses a common Ethernet LAN cable, instead of a single twisted pair cable, to communicate with the PBX. An illustrative LAN-PBX system is shown in FIG.
3
. In this case, the PBX is actually a telephony server
27
with switch control software that is connected to the LAN. The telephones
21
,
23
and
25
are Ethernet LAN devices that also communicate over the LAN. Thus the telephony application, consisting of telephones
21
,
23
, and
25
, and a telephony server
27
, attached to a WAN interface
28
, can utilize the same switch
22
as the computers
24
and network data servers
26
. The advantage of the LAN-PBX architecture shown in
FIG. 3
is that the telephones
21
,
23
and
25
can use the same wiring and data switches as are used to convey LAN data, thus resulting in increased flexibility and overall lower cost.
A significant problem with the LAN-PBX approach illustrated in
FIG. 3
is that telephony data has different delivery requirements than normal computer and server data. Telephony data must be delivered on-time (within a few milliseconds), and without delay, on a continuous basis. Normal computer data can usually suffer delays of a few hundred milliseconds without difficulty. Delays of this magnitude (a few hundred milliseconds) are common in computer networks. They occur because computer data is transmitted at a variable and unpredictable rate. As a result, there can be momentary blockages and congestion, even though the network has adequate bandwidth for the average data load.
Existing LAN-PBX systems attempt to solve this problem by giving telephony data priority over computer data. In the event of data congestion, such existing systems pass telephony data ahead of computer data. This priority system can work when only one telephone with data to transmit is present on a given circuit at a given time. However, when a circuit must carry multiple telephone connections, the congestion problem can arise again. This happens because multiple packets with equivalent priority give no means for arbitration. Consider the Telephony Server Link
30
shown in FIG.
3
. When multiple telephone calls are placed to the WAN interface
28
they must all pass through the link
30
. In that event, multiple telephony data packets, all having equivalent priority, may simultaneously require shared telephony server link
30
resource. A priority mechanism cannot distinguish between them, and the packets cannot interfere with one another.
Another problem with the LAN-PBX is that Ethernet cables and switches make no provision for providing power. Generally, in an Ethernet-based system as shown in
FIG. 3
, power is provided by a separate telephone power supply
29
at each station or instrument. As a result, it is difficult to operate the entire network in the event of a power outage. The user must provide backup power at each instrument, instead of centrally, as is possible with a typical PBX system.
Additionally, both PBX and LAN-PBX systems have difficulty supporting multiple types of instruments, in a flexible manner. Some instruments need many features, while others need only basic capabilities. There is no convenient way to extend or modify an instrument's behavior without complete replacement. That is, accessories to instruments are rarely supported.
Typical existing PBX systems, such as the one illustrated in
FIG. 2
, suffer from another problem. The telephone number of a particular handset is determined by the circuit jack to which it is attached. This is inconvenient, as users may need to move a handset from one jack to another, while maintaining the same telephone number. Under such circumstances, the typical PBX user must reconfigure the switch.
Finally, existing LAN telephones are operated by internally stored control software. Such software must normally be installed separately into each instrument. This procedure makes software updates and corrections difficult, since each instrument must be reloaded individually.
For the reasons stated above, it would be desirable to have a LAN telephone instrument system which uses the same wiring system as is used to convey data transmission, and which operates without the delays that may occur in existing systems. It would further be desirable to have a LAN telephone instrument system which a) operates using power supplied over Ethernet cables, b) provides for accessory attachments, c) can maintain a phone number even when moved to a new jack, and d) enables convenient downloading of software.
BRIEF SUMMARY OF THE INVENTION
Consistent with the present invention, a LAN telephone instrument is disclosed. The disclosed LAN telephone uses a Time-based Routing (TBR) technique to schedule packets of voice-telephony data. Through use of the Time-Based Routing technique, the problems of multiple LAN telephone instruments sending contending or colliding packets is avoided. The disclosed LAN telephone operates in connection with a system for providing power to the LAN telephone instrument through an attached LAN cable. This allows multiple LAN telephone instruments to be centrally powered.
The disclosed LAN telephone further includes a technique for automatically providing a remote switch with location of the LAN telephone instrument, thus enabling automatic direction of calls thereto. Additionally, a system for remote configuration of the control program of a LAN telephone instrument is also disclosed, which employs the LAN itself to provide the data connection over which the control program is downloaded.
The present disclosure further includes a system for attachment of telephone instrument accessories, which may be used to extend the functional capability of the LAN telephone instrument. An illustrative accessory, an operator console, is described in detail.


REFERENCES:
patent: 5526353 (1996-06-01), Henley et al.
paten

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