Call forwarding reprogramming device

A device attached to a subscriber telephone line is programmed to automatically initiate conference calls connecting two other telephone lines, using the three party custom calling feature offered by modern phone systems. Numbers of the two other telephone lines to be connected may be entered from a remote location.

BACKGROUND OF THE INVENTION 
The present invention relates to a method and device for remotely 
controlling call conferencing on a telephone line. 
Call conferencing now exists as a standard option for telephone users. At 
the present time, a user with the call conferencing option on his 
telephone line, otherwise known as the three party calling option, must 
initiate a conference from his telephone instrument. A conference call is 
initiated by calling a first telephone number, then tapping on the switch 
hook of the telephone until a second dial tone is heard. Then a second 
number is dialed. Then the switch hook is tapped once again. At this point 
a three way call exists between the telephone user and the two numbers 
which he dialed. 
However, it would be useful for telephone users to be able to initiate a 
three party call from a telephone at which they are not present. For 
example, if the telephone subscriber is away from his home and at a public 
telephone, it would be helpful if he could arrange to have the public 
telephone and another phone connected via the conference facility 
installed on his home telephone. By doing this, the subscriber could avoid 
the need to put a large number of coins into the pay telephone for a long 
distance call. Rather, it would be his home telephone that would initiate 
the long distance call. Thereafter, the three party calling feature would 
be used to connect the home telephone to the pay telephone. 
This use of the three party feature, made possible by remote programming, 
is a substitute, in many cases, for a telephone credit card or other 
payment means. 
SUMMARY OF THE INVENTION 
The main object of this invention is to provide means for using the three 
party calling feature in order to connect two telephones, A and B, via a 
third telephone, C, which is equipped with the three party calling 
feature. This is accomplished by placing a remote control device at C 
which can imitate the actions of a person at C who desires to initiate a 
conference between A and B. The remote control device may be instructed to 
initiate a conference by a person calling from A or B.

DETAILED DESCRIPTION OF THE INVENTION 
This device acts to connect telephones A and B via three party calling 
service available at telephone C. A and B are separate telephone numbers, 
and can be any number that could be connected in conference from telephone 
C using the three party calling feature. The invention operates without 
the need for someone to be present at the site of telephone C. Upon 
detection of a ringing signal incoming on the line of telephone C, the 
device will automatically answer the telephone and listen for signals 
which instruct the device regarding which two numbers are to be connected 
in a conference. These signals could be generated by a person at telephone 
A. Thereafter, the person at telephone A hangs up, and the device releases 
telephone line C. The device then places signals upon telephone line C 
such that a conference is established between line C, B, and A. Thus, the 
persons at telephones A and B may communicate via C, without the need for 
anyone to be at the site of telephone C. 
An embodiment of this invention is shown in FIG. 1. Telephone line C is 
connected to the device. When a person calls telephone line C, ring detect 
circuit 1 changes the state of the I/O line connected to microcomputer 
chip 4. Chip 4 is programmed so that another I/O line, suitably buffered 
by buffer 5, causes relay 2 to close. Line relay 2 completes the current 
path between the telephone line connectors and causes the telephone line 
to go into the off hook state. DTMF receiver chip 3 listens on the line 
for signals. As valid DTMF signals are detected, they are made available 
on the output of DTMF receiver chip 3. This output data is stored in the 
memory of microcomputer chip 4. 
Then, the caller could type an ID code of, for example, 4 DTMF digits. 
Then, the caller could type in DTMF signals indicating the phone where he 
is at. At the end of this sequence of digits, he could press the # button 
on his phone in order to delimit the number. Thereafter, he could enter 
the number of the other phone to which he wished to be connected. He could 
also follow this number with the # button. 
The program in the ROM of chip 4 will examine the sequence of DTMF digits 
that is received. If the ID code is correct, and there are two #'s in the 
sequence, then the device could send an acknowledge beep to the user. The 
beep could be generated by DTMF generator chip 5, connected to chip 4's 
I/O lines. 
Thereafter, chip 4's program will cause line relay 2 to open and release 
the telephone line. Then chip 4 will cause relay 2 to be closed again. 
First, chip 4 will key DTMF generator 5 in such a way that the number of 
telephone A is put onto the line. After A has been dialed, chip 4 causes 
relay 2 and the DTMF chip to do what is required to connect line B using 
the third party calling feature. 
Typically, what is required is for the flow of current in telephone line C 
to be briefly interrupted . . . so that the action of a person tapping on 
the switch hook of a telephone is imitated. Chip 4 can do this by causing 
relay 2 to open for a brief moment. 
In the best mode of this invention, dial tone detector chip 6 monitors the 
result of the switch hook tapping imitation. If the simulated tapping by 
relay 2 is successful, chip 6 will indicate via an I/O line to chip 4 that 
dial tone is present on the line. If the simulted tapping is not 
successful, chip 4 is programmed so that different patterns and lengths of 
tapping are tried until such time as dial tone is detected. 
When dial tone is detected, chip 4 keys the second telephone number into 
DTMF generator chip 5. 
Then, following what is common protocol required by the three party calling 
feature, relay 2 imitates a switch hook tap again. This connects the two 
lines together. 
Actual part numbers that will operate in FIG. 1 are as follows: an 8748 
microcomputer; and 8870 DTMF receiver; a 5088 DTMF generator; and a 567 
dial tone detector chip. Relay buffer 5 can be several sections of a 4049 
buffer tied in parallel. 
The ring detect circuitry shown in FIG. 2 comprises an optoisolator chip. 
High ringing voltage peaks cause current to flow through the LED of the 
optoisolator. These, in turn, change the state of the I/O line. 
Many alternate schemes exist for accomplishing the goal of this invention. 
For example, rather than using DTMF signals for number of ID input, voice 
recognition technology could be used. Furthermore, if the user knew in 
advance what lines he wished to connect in a conference, a pre-set pair of 
numbers could be stored in the device. 
The device could also be set up to sponstaneously initiate conferences 
using stored numbers at a given time of the day, or upon the occurance of 
some other condition. 
Discrete components could accomplish the functions of the device. In fact, 
the numbers dialed could be simply recorded by an analog device such as a 
cassette recorder and played back into the phone, rather than being 
recieved by a DTMF reciever, stored, and later output by a DTMF generator. 
Upon ringing of line C, a relay would answer the phone and a casette would 
record the digits of two telephone numbers separated, say, by a press of 
the * button. After the caller had hung up, the device would take the 
phone off the hook again and simply play back into the phone line. A tone 
detector connected to the line would listen for the * tone separating the 
numbers. When this was heard, the detector would cause the line relay to 
briefly open the line . . . as an imitation of the switch hook tap. Then 
the cassette would proceed to play the second number into the line. At the 
end, the device would cause a second tap to occur so that the three party 
calling protocol is satisfied. This could be accomplished by the caller 
having inserted a second * on the cassette at the end of the second 
number. 
Once a conversation is finished, it is necessary to assure that the device 
will release line C. This can be causing the device on line C to reset to 
a given state upon receipt of a certain pattern of DTMF digits. For 
example, at the end of the conversation, one of the callers could simply 
hit the # button. 
Alternatively, the device could reset when it heard dial tone. This would 
indicate that the callers had hung up. Or, the device could also include a 
circuit that monitored the level of speech energy on the line. When speech 
ends, the device would reset. 
Thus, the essence of this invention is not only a particular device. It is 
most broadly a new use for the three party calling feature: connecting two 
phones via a non-manned telephone, using instructions supplied either by a 
person at a remote site, or by a pre-set program at the non-manned 
telephone.