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Description  |
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BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to telecommunications networks and in
particular to telephone networks including facilities for carrying out,
telemetry or remote control functions.
2. Related Art
The cost to utility companies, such as gas, electricity and water
suppliers, of manually reading meters is substantial. Consequently, meters
are read infrequently and householders frequently receive estimated
accounts rather than those based on actual consumption. Further difficulty
can arise where meter readers are unable to obtain access.
Thus, remote meter reading is desirable although the high capital cost of
installing a communications network specifically to read utility meters,
particularly retrospectively, may not be justified. In the past, some
remote controlled operations have been carried out using dedicated
telephone links through public switched telephone networks. However, such
usage of dedicated telephone numbers for use say once a month could not be
justified.
Accordingly proposals have been put forward by the present applicant and
others to use existing telephone network connections to customer premises
to carry out various remote control and/or telemetry tasks. One problem
with such proposals is that such usage of the telephone network could
adversely affect network telephony traffic or other services offered over
the network. For example there may be regulatory requirements regarding
availability for telephone calls. Also, if there are tariff differentials
between network uses for different purposes, a network operator will wish
to give priority to the network use which generates the higher revenue.
Also calls such as telemetry calls will normally be less time sensitive
and therefore of lower priority than, say, a telephone call which may
relate to potentially life-threatening circumstances.
SUMMARY OF THE INVENTION
According to a first aspect of the present invention there is provided a
telecommunications switching network including a multiplicity of
connections to consumers premises, at least some of said connections being
co-terminated by both telecommunications apparatus and telemetry interface
means, the network providing a first alert signal to cause the
telecommunications apparatus to respond and a second, different alert
signal, to cause the telemetry interface to respond characterised in that
the switching network includes control means responsive to network signals
indicating a telecommunications call attempt to force release any
telemetry call then in progress.
According to a feature of the first aspect of the invention, the telemetry
interface is responsive to a change in line characterisation indicating
attempted operation of co-terminated telecommunications apparatus to
forward signals to the switching network to cause any telemetry call in
progress to be aborted.
According to a second aspect of the present invention there is provided a
telephone switching network including a multiplicity of connections to
consumers premises, at least some of said connections being co-terminated
by both telephony apparatus and telemetry interface means, characterised
in that the switching network includes control means responsive to signals
indicative of telemetry call to override any class of service indicating
barring of incoming calls to the telephony apparatus.
In this specification, the term "telemetry interface" is used to refer to
an interface which is associated with utility meter(s) and/or other
devices such as heating systems, electrical apparatus etc. which are
subject to remote control. If there is to be no reading of utility meters
the interface may not, strictly speaking, be facilitating any telemetry
(i.e. remote reading) but nevertheless, the interface is still referred to
as a "telemetry interface".
BRIEF DESCRIPTION OF DRAWINGS
A telephone network in accordance with the invention will now be described
by way of example with reference to the accompanying drawings of which:
FIG. 1 is a schematic diagram of a telecommunications network according to
one embodiment of the invention;
FIG. 2 is a schematic diagram of an embodiment of a consumer premises
installation in the network of FIG. 1; and
FIG. 3 is a schematic diagram of an embodiment of the telemetry interface
of FIG. 2.
BRIEF DESCRIPTION OF EXEMPLARY EMBODIMENTS
Referring to FIG. 1, in a typical public switched telephone network (PSTN)
operating in a digital switching environment there will be a number of
digital main switching units 1 (DMSU) (only one of which is shown) fully
interconnected to provide full switching capability. Each DMSU 1 is
connected by way of a digital network 5 to a number of local exchange
units 2 which supply telephony service via local network connections 3 to
consumer premises 4.
Each of the local exchange units 2 is responsive to a Network Management
control system 6 to set up telephone calls, determine facilities available
to consumers and to effect billing and other services. The Network
Management system 6 will have input from customer service records system 7
to determine (for example) whether incoming or outgoing calls are
permitted to particular consumer premises. Records system 7 also records
the presence of telemetry service for each consumer line, and keeps
records updated, logs faults and contacts the customer when these are
cleared. The Network Management System 6 also influences the operation of
the DMSUs 1.
Telemetry service platform 8 can operate on behalf of utilities 9 (e.g.
gas/electric/water companies ) to effect remote readings of utility meters
located at consumer premises 4. Telemetry platform 8 can be instructed to
"read" a number of meters in different premises 4 and subsequently forward
a "batched" report of the meter readings. Telemetry platform 8 is a
stand-alone platform in the network, which has the ability to control the
initiation of telemetry or other remote control calls, and can perform the
necessary associated functions, such as scheduling and traffic management.
The telemetry platform communicates with a telemetry service management
system 81 (TSMS) which carries data requirements for remote meter
reading/function control.
TSMS 81 incorporates the following data elements:
consumer reference number;
directory number--so that calls from a consumer's premises can be routed to
the utility across the network; updated automatically with consumer
changes by customer service records 7;
utility data--enabling a check of which utility is responsible for a
particular consumer's meter (51);
type of telemetry interface 14 (FIGS. 2, 3)--TSMS 81 needs to instruct
platform 8 how to access different types of interface, together with
information on appropriate `wake up` tones;
telemetry interface address/port number--the platform 8 will need this to
complete the call set-up phase with an interface 14;
interface owner--may be the network operator, the utility or a separate
company--will be sent fault reports in the event of failure of an
interface 14;
security component--the link from the platform 8 to an interface 14 may
require an authentication process or encryption;
billing address--instructs TSMS 81 where to direct the meter reading.
TSMS 81 may also maintain data on consumers for bulk read operations. This
could be held against each consumer's record or could be stored as a list
in the TSMS. TSMS 81 will also record the message, supplied by the utility
or other `owner` of meters 51 or remote control devices 61, which is to be
sent to the meter/device as part of the reading/control operation.
TSMS81 has a number of functions:
receives new customer enrolment and cessation requests for telemetry/remote
functions;
maintains a failed call log;
provides billing information to billing database 83;
monitors quality of service;
maintains archive data for an agreed interval;
receives and processes results from the telemetry platform 8 and returns
results to the utilities 9 together with their customer references or
telemetry interface 14 identity information;
maintains details of "wake up" tones for each interface 14.
FIG. 2 shows an installation in a consumer's premises 4. Referring to FIG.
2, connected to the line 3 by way of a suitable network termination 10 a
customer may have normal telephony apparatus such as telephone 11 and
answering machine 12, and other apparatus for telecommunications services
such as a modem for a personal computer or facsimile transmission
apparatus (not shown).
Other functions which share the telephone line 3 may include home security
apparatus 13 which provides connection to remote monitoring stations if
(e.g.) fire detectors or intruder detectors are in use.
In addition, the consumer premises has a telemetry interface 14 which has
connections 15 to interface circuits of gas, electricity or water meters
51 for example and also connections 16 to switching controls 61 for use in
remote operations such as switching on and off heating systems and the
like.
The telemetry interface 14 monitors the line 3 for a "wake-up" tone
dedicated to telemetry operation. Further detail of the monitoring may be
obtained by reference to our co-pending European Patent application no
(A24784) filed on Apr. 13, 1994.
The telemetry interface 14 does not require ringing current to be supplied
from the exchange (2 of FIG. 1) so that other telephony apparatus 11, 12
is not affected by telemetry calls set up through the network. Thus meter
reading can occur without the consumer's knowledge or disturbance. Calls
controlled by interface 14 are referred to as "no ring" calls, since they
occur with no call arrival indication (e.g. ringing current) to the
consumer.
FIG. 3 is a block schematic diagram of telemetry interface 14. Thus,
referring to FIG. 3, within the telemetry interface 14 a power supply 17
may draw power from the telephone line 3 to operate other circuits
including a tone detection circuit 18. The tone detection circuit 18 is
tuned to a particular frequency or frequencies to monitor the line 3 for a
"wake-up" tone. If a wake up tone is detected then the tone detector
forwards an interrupt signal to a microprocessor 20 causing it to commence
telemetry operation.
By way of an input 19 the microprocessor receives subsequent tones from the
line 3 to cause it either to forward operating signals to the connections
16 to various remote control functions 61 or to forward a request signal
to utility meters 51 by way of connections 15.
If signals are to be returned from utility meters to the telemetry platform
(8 of FIG. 1), the microprocessor 20 receives data by way of connections
15 and forwards the data by way of a signal generator 21 to the telephone
line 3.
An impedance detection circuit 22 is also provided in the telemetry unit.
If this circuit detects a change in line impedance (or line voltage)
indicative of other apparatus (e.g. telephone 11, security unit 13)
looping the line then it causes the signal generator 21 to remove a
pre-determined indication of presence (for example a channel tone) from
the line 3 which causes the telemetry platform 8 (of FIG. 1) to abort its
connection through the network to the consumer's premises 4. Thus
telemetry operations do not take place if there is an alternative
requirement for line usage at the consumer premises 4 and telemetry
operations remain transparent to the telephony customer.
Referring again to FIG. 1, while a telemetry call is in progress, if the
local exchange unit 2 receives a network signal indicative of an incoming
telephone call for consumers premises 4, it will cause the telemetry
connection to be abandoned and will signal the telemetry platform 8
accordingly such that normal telephony will occur again maintaining
transparency of the telemetry operation.
The process of operation of the embodiment of the invention illustrated in
the drawings will now be described in more detail.
TSMS 81 initiates a meter read operation in line with a utility's
requirement. This may be a pre-specified bulk read of an identified group
of that utility's customers. As indicated above, the TSMS 81 may have
these customers' records marked accordingly.
Telemetry platform 8 completes the calls to the interfaces 14. It receives
telemetry requests from TSMS 81 together with the information needed to
complete the call--i.e. the consumers' directory numbers, wake-up tones
etc. For each telemetry call to be made, a no-ring call request is made to
DMSU 1 via CCITT Signalling System No. 7 (C7) in conjunction with a
pre-determined embedded protocol.
In the event that the line is already engaged (i.e. an `off hook`, looped
or engaged status is detected) then the request is not accepted and a
signalling message is returned, causing the platform 8 to reschedule the
call and re-try later. Rescheduling and re-trying will then occur up to a
specified maximum number of times--e.g. two re-tries the same night
followed by a number of consecutive night-time attempts, and finally a
day-time attempt.
The local exchange 2 is arranged so as to override a range of network
services such as call diversion and call barring.
Once an answer indication is received by the local exchange unit 2 from the
interface 14, a normal speech path is established between the telemetry
platform 8 and the interface 14. The local exchange will clear the call in
the normal way on receipt of a request from the telephony platform, or if
the call is timed-out, or in the event of another incoming or outgoing
call. It is noted that the answer indication may be establishment of a
loop condition or by predetermined in band tone signalling such as DTMF
signalling.
The no-ring call needs to occur without interfering with the consumer's
other telecommunications services in any way. Therefore a consumer needs
to be able to make and receive incoming or outgoing calls. Incoming
callers should hear ringing tone during a call attempt, even if a no-ring
call is then occurring, and the consumer should hear dial tone whenever he
wants to initiate a call.
A no-ring call of the kind which causes a loop answered condition prevents
the local exchange 2 from recognising a call attempt by the telephony
customer. Thus the telemetry platform 8 monitors the signal level of the
data channel during the no-ring call. If there is a drop in the signal
level--typically around 4 dB, this is indicative of such a call attempt.
The platform then sends a priority force release message to the local
exchange 2 to release the no-ring call. The priority force release
signalling message (using CCITT No 7 signalling as referred to above) also
instructs the local exchange unit 2 to maintain the connection to the
consumers premises 4 and to supply dial tone to the line 3. TSMS 81 is
notified to re-try the no-ring call at a later time.
It will be appreciated that in certain circumstances calls to specific
consumer's premises 4 are not permitted. Thus, during customer absence for
example, a request for temporary call barring may be placed. Such
information is available to the Local Exchange 2 by virtue of periodic
updating from the Network Management System 6 and is normally known as
class of service information.
On request for a call set up, the local exchange 2 will consult the class
of service information and, if that information indicates that calls are
not permitted, will prevent establishment of a call through the network.
However, if the call is for remote meter reading for example, the local
unit will override the class of service restriction and cause a no-ring
call to be established for that purpose. Calls for service for other
purposes (e.g. for remote operation) may still remain barred.
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