Note: Descriptions are shown in the official language in which they were submitted.
CA 02309531 2000-OS-25
1
METHOD TO INTERFACE A CELLULAR (WIRELESS) TELEPHONE TO A
STANDARD TELEPHONE SET
Field of the invention
The present invention relates to a method and apparatus to interface a
wireless
device to a standard telephone set. More particularly, the present invention
relates to such a method and apparatus to interface a cellular telephone to a
standard telephone set.
Description of the prior art.
Cellular phone are now quite common. In fact, such telephones, and other
wireless devices, are becoming so popular that some people do not see the need
for standard, land-line telephones within a house. Indeed, the cost of
operating a
cellular phone has decreased to the point that it is competitive with local
service.
Some of the disadvantages of replacing standard telephone lines with wireless
units are that the wireless device must always be carried with the user and
eventually recharged. Also, there can only be one handset per phone number in
cellular technology, as opposed to standard telephone service where many
handset can be associated with a single telephone number.
There is consequently a need for a method and device to interface a wireless
device to a standard telephone set.
Summary of the invention
The present invention is directed to a method and device to
interface/interconnect
a cellular telephone to a regular telephone set circuit that is disconnected
from the
C.O. (Central Office).
CA 02309531 2000-OS-25
2
Such a device and method can be used for forwarding incoming and outgoing
calls
to a cellular telephone.
Advantages
~ Reuse of existing standard telephone wiring in buildings
~ Eliminate the costs associated to regular telephone lines.
~ Extend the life of standard telephone sets in a world going wireless.
~ Isolates the user from exposure to cellular telephone radiation.
~ Convenient in being able to answer incoming calls from any standard
telephone set when a cellular telephone is plugged in the proposed cradle
device.
~ Convenient in not needing to remove cellular telephone from charger when
answering calls.
~ Can potentially save long distance costs (when used in an adjacent calling
area).
Preferably, the cellular telephone interface will be very similar to an
existing
charging stand. Basically the phone would sit in a cradle. The cradle would
have
the possibility to hold multiple telephones, but with one being the main slot.
Each
slot will be able to recharge independently its associated telephone battery.
The
cradle would then simply be plugged in any RJ-11 jack.
The device is composed of (3) three major components:
1. The cellular telephone interface, with its main function of
communicating and controlling the cellular telephones activity;
2. The analog phone circuit, with its main function of simulating CO
(Central Office) features, such as power supply, distinct ring signal, dial
tone,
sensing on-hook and off-hook of a standard telephone set;
3. The micro-controller, with its main function of monitoring activity on
both interfaces (Cellular and analog telephone interfaces) and assuring proper
sequencing of actions upon reception of events.
CA 02309531 2000-OS-25
3
The cellular phone interface circuitry is composed of a physical connection
between the cellular telephones and the micro-controller component. This is
achieved with the use of a connector that fits into the cellular telephone
external
connector. The main functions of the interface will be to physically connect
the
cellular telephones to the micro-controller, send commands to the cellular
telephones, receive status information from the cellular telephones and
finally
redirect the audio TO and FROM the cellular telephones. The type of status
information being received from the cellular telephones will look as follow:
(Telephone is available, telephone is ringing, telephone is attempting to
establish a
call). Typical commands that will be sent to the cellular telephones will look
as
follows: (Answer incoming call, Release call, Dial a number). The
communication
between the cellular telephone and the micro-controller is done through a
proprietary protocol supplied by the cellular telephone manufacturers
(Motorola,
Nokia, Ericsson, etc..). The secondary function of the interface is to also
provide a
battery charging feature.
The following procedures can be used within the context of the present
invention.
1. Outgoing call
The cellular telephone that is in the master slot will receive a command from
the
micro-controller to attempt to establish a call. When the call is finished
(All
standard telephone sets are on-hook) the micro-controller will signal the
cellular
telephone to end the call. The protocol and command formats sent to the
cellular
telephone are proprietary information provided by the cellular telephone
manufacturers.
2. Incoming call
The micro-controller will be continually polling all the cellular telephones
status to
detect any incoming call. The protocol and status information formats received
from the cellular telephones are again proprietary information provided by the
cellular telephone manufacturers.
CA 02309531 2000-OS-25
4
The Standard Telephone Set Interface
The standard telephone set interface circuitry is composed of a physical
connection between the "house" wiring via RJ-11 jack and the micro-controller
component housed in a cradle shape container. The main functions of the
standard telephone set interface are to be implemented by a few circuits that
basically simulate the functions of a CO (central office). The interface is
broken up
into four more components.
1. A ring generating circuit that generates the 90Volt RMS at 30Hz to
the telephone set;
2. A dial tone generating circuit that supply a dial-tone when a standard
telephone set is detected off-hook.;
3. A power supply to supply the 45Volts to the line and all the
components;
4. A DTMF decoder circuit to decode DTMF signals and convert them
to a binary format; and
5. Finally a SLIC integrated circuit to patch audio signals and detect
standard telephone set act1 ivity.
1. Outgoing call
When the standard telephone set is off-hook, the standard telephone interface
signals the micro-controller through the interface circuitry. This is achieved
with
the use of a SLIC (Subscriber Line Integrated Circuit) and an oscillator
circuit a
dial tone type frequency signal to the telephone set. The interface will then
decode the dialed numbers with a DTMF (Dial Tone Modulated Frequency)
decoder circuit and forward this data in a binary format to the micro-
controller for
parsing and temporary storage. The program stored in the micro-controller will
parse the number and determine when to send the complete number to the
Cellular telephone interface.
CA 02309531 2000-OS-25
2. Incoming call
When an incoming call is sensed on one of the connected cellular telephones,
the
standard telephone set interface will receive a signal from the micro-
controller to
start it's ringer circuit with it's associated distinct ring. This state will
be maintained
5 until the micro-controller receives an off-hook signal from the standard
telephone
set interface or other conditions originating from the cellular telephone
interface is
reversed. The off-hook sensing is achieved with the SLIC integrated circuit,
the
output is a TTL high signal forwarded to the micro-controller.
The Micro-Controller Module
The micro-controller module is composed of a micro-controller unit, memory and
input/output communication channels. The main function of the module is to
monitor events and start or stop actions on the associated interface circuits.
The
micro-controller will be programmed on an event driven programming paradigm.
In other words, when an event is detected, an action or multiple actions will
be
executed.
The micro-controller will be programmed to continually monitor cellular
telephone
activity. The program will poll the cellular telephone interface for activity
and
trigger the standard telephone set interface. The same polling principle would
apply in the case the standard telephone set activity would be detected.
1. Outgoing call
When the standard telephone set is off-hook, the micro-controller receives a
signal
from the standard telephone set interface. This means that an outgoing call is
being initiated. The micro-controller will trigger the dial tone generating
circuit and
prepare to receive numbers in a binary format sent from the DTMF circuit. When
the first number is received, the micro-controller will trigger off the dial
tone
generating circuit. Afterwards, as numbers are received into the micro-
controller,
a program stored in the micro-controller will parse and analyze the number.
The
program stored in the micro-controller will parse the number and determine
when
CA 02309531 2000-OS-25
6
to send the complete number to the Cellular telephone interface. Once the
program determines the number is complete, it formats and sends it in the form
of
a command to the cellular telephone interface. The micro-controller will then
trigger the Audio amplifier circuit on. The micro-controller will then wait
for an on-
hook signal to issue a "release call" command to the cellular telephone
interface.
2. Incoming call
When an incoming call is sensed on one of the connected cellular telephones,
the
micro-controller will receive this status information. It will then proceed to
trigger
the ringer circuit with it's associated distinct ring. The micro-controller
will then
wait for a off-hook signal from the standard telephone set circuit. If a off-
hook
signal is received, the micro-controller will then send a pick-up call command
to
the cellular telephone. Finally, the micro-controller will trigger the Audio
amplifier
circuit on. The micro-controller will then wait for an on-hook signal to issue
a
"release call" command to the cellular telephone interface.
Brief description of the drawin4s
The present invention will be better understood with the help of the following
drawings, in which:
Figure 1 is a schematic representation of the interface within a system;
Figure 2 is a schematic representation of the main components of the
interface device according to a preferred embodiment of the present invention;
Figure 3 is a schematic representation of the decoder circuits;
Figure 4 is a schematic representation of the interconnection of the micro-
controller; and
Figures 5 and 6 are state transition models for an incoming call data flow
diagram and an outgoing call data flow diagram, respectively.
