Note: Descriptions are shown in the official language in which they were submitted.
1 1703~3
This invention relates to a telephone for use by
a physically handicapped person.
In 1981, attention has focused on the handicapped
and, in particular, ways in which the handicapped person's
environment may be altered to enable the person to overcome the
apparent limitations imposed by the particular handicap.
Operation of a conventional telephone can be a
fairly daunting task for a person with severely limited motor
ability, for example, a para- or quadriplegic. The operations
involved in participating in a telephone call are initiation,
receiving and termination of the call. Analyzing these operations
from the point of view of calling and called party movement, the
handicapped person must station himself close to the telephone set,
must lift the telephone handset to operate the hook switch, must
dial a number if he is the calling party, must hold the handset
in a position to both hear and speak, and, lastly, must return
the handset to the telephone cradle. For a severe physical handicap,
the series of operations may be impossible. The present invention
proposes a circuit for use in a telephone system which will enable
easy and effective use of the telephone system by such a handicapped
person.
According to the invention, there is provided a
call sequence control circuit for use in a telephone system, the
circuit comprising:-
a transducer;
switch means under the control of the transducer
operable to make and break an electrical connection between a
telephone speech circuit and the telephone line;
- 1 - ~
1 170383
signal generating means under the control of the
transducer for generating a signal representing a predetermined
telephone number and for transmitting the signal to the line;
detector means for detecting ringing voltage on
the telephone line; and
control means for preventing transmission of said
signal while ringing voltage is being detected by the detector
means.
The switch means preferably includes a primary
switch which controls both the operation of the signal generating
means and the actuation of a relay controlled telephone hook switcho
The circuit preferably includes means for establishing
a delay between operation of the hook switch and operation of the
signal generating means in order that dial tone can be established
from a telephone central office. The transducer can include a
diaphragm switch operated by a pressure differential caused by a
telephone user blowing or sucking into the transducer~ The
transducer can, alternatively, be an impact or touch switch.
The signal generating means is preferably adapted to produce zero
dialling so as to contact the telephone operator to whom verbal
instructions can be given for placement of the call. The signal
generating means and the detector means should be connected to
the telephone line via optical isolators. The isolators prevent
noise and high current surges from appearing on the line.
The telephone speech circuit preferably includes a
microphone mounted on a movable boom. It can also include any one
of a loudspeaker, an earphone, or a headset.
1 170383
An embodiment of the invention will now be
described, by way of example, with reference to the accompanying
drawings in which:-
Figure 1 is a block diagram showing the essentialelements of a telephone call sequence control circuit according
to the invention;
Figure 2 is a circuit schematic diagram showing the
blocks of Figure 1 in more detail; and
Figure 3 shows a telephone for the disabled
incorporating the circuit Or Figure 1.
Referring particularly to Figure 1, the circuit
consists of a transducer 10 and a controller 12 connected to the
transducer. The controller functions to operate a hook or line
~witch 14 to connect a voice circuit 16 to line 18 to initiate a
call, and to disconnect the voice circuit from line to terminate
the call. The controller 12 also controls a signal generator 20
which produces a dialling signal to the line 18. Lastly, a ringing
voltage detector 22 detects ringing voltage on the line associated
with an incoming call and while ringing voltage exists, prevents
signalling data from going to line for a predetermined period after
the transducer 10 is operated
Referring in detail to Figure 2, the transducer 10
includes a diaphragm 24 which is distorted, when a sufficiently
high pressure differential is produced in a chamber 26, to operate
switch contacts 28. Such a transducer is available from Fairchild
Corporation under the Specification No. PSF106-1.5H. The switch
contact pulse actuates a monostable 30 having a 22 ms delay so as
to remove switch contact bounce. One output of the monostable 30
I 1 70383
is taken to a flip-flop 32~ The flip-flop produces an output in
response to every input pulse. The flip-flop output is coupled
via an inverter 34 to the base of a transistor 36 which is series
connected to a relay 38. The relay controls the telephone
"hook switch" 14 to make and break a connection between the
telephone line and the telephone speech circuit.
Another output from the monostable 30 is taken to
a second monostable which establishes a longer delay of 400 ms.
The output from the monostable 40 is taken via an inverter 41
to a NAND gate 42, an output from which controls a transistor 44.
When the transistor conducts, an optical isolator 46 switches
the output of an E-Digipulse (RTM) integrated circuit to the
telephone line. The E-Digipulse circuit is a standard integrated
circuit utilized on a telephone circuit PCB 48 available from
Northern Telecom under specification NoO QDN 35 BX and is used to
produce dial pulse signalling from keypad or other non-rotary dials.
As indicated, two of the Digipulse terminals are strapped together
so that the circuit outpulses only a single "ZERO" indication for
every input pulse to the circuit. The 400 ms. delay before
"ZERO" outpulsing ensures that in normal circumstances the central
office receiving equipment has been readied to receive signalling
information. When the "ZERO" indication is received at the central
office, the telephone operator establishes a voice connection with
the telephone user, thereby automatically switching out the E-
Digipulse circuit. Once voice communication has been made, the
telephone user states the particular number that he wishes to reach
and the connection is made by the operator.
1 170383
Call termination is achieved simply by operating
the transducer 10 again, the flip-flop output then causing the
relay 38 to drop out and to restore the "hook switch" to an
"on hook" position in which the connection between the voice
circuit and line is broken.
The circuit illustrated in Figure 2 is also adapted
to handle an incoming call. A low voltage output, generated from
ringing voltage by a voltage tap, is directed to an optical
isolator 50 when ringing voltage is present. The voltage tap
includes a capacitor 52 to prevent operation in response to DC
and low voltage signals. A zener diode 54 conducts when ringing
voltage (80 V RMS), is present. The optical isolators 46 and 50
are standard units incorporating a light emitting diode and a
phototransistor. The output from the optical isolator 50 is taken
to a monostable 56 which, for a period of 5 seconds after the
start of each ringing burst, disables the NAND gate 42. Since the
ringing voltage bursts have a duration of only 4 seconds, this
means that the NAND gate will not operate while ringing voltage
is present. Thus even if the transducer switch is operated by
the handicapped user, there is no "ZERO" outpulsing to the central
office. Operation of the transducer switch merely causes the
"hook switch" to go "off hook", so establishing a voice path.
As illustrated in Figure 3, transduction features
of the voice circuit are also adapted for use by the handicapped
telephone user. Thus, the telephone instrument has no conventional
handset, but instead has jacks 55, 57 and 59 respectively for a
plug-in transmitter unit, receiver unit, and transducer switch unit, the
1 170383
jacks providing the opportunity of several options depending on
the nature of the handicap and on the handicapped person's
surroundings. In the particular example shown in Figure 3, the
transmitter unit has a microphone 58 mounted on a flexible boom
60 and the receiver unit incorporates a loudspeaker 62 housed
in a base set cabinet 66, and controlled by volume knob 68.
As shown in Figure 3, a tube 64, forming part of an oral
transducer, is also mounted on the boom 60.
In order to preserve some privacy in the event that
the handicapped telephone user desires it, there is optionally
provided a lightweight headset (not shown) incorporating a
microphone and receiver and a combination plug for insertion in
jacks 55 and 57.
Although the particular call sequence control circuit
is described and shown in conjunction with a transmitter and
receiver features particularly adapted for the handicapped, it need
not be so limited. Thus, for example, much work is being done in
speech recognition and interpolation systems. A call sequence
control circuit of the type described can be adapted to take
advantage of state of the art speech recognition equipment. Thus,
the transducer 10 of Figure 1 could include a speech interpolation
unit and the controller can be adapted to produce a data control
signal to the signal generator to prompt the automatic generation
and transmission of any telephone number. In use, verbal
instruction is monitored by the speech interpolation unit which has
an output to the controller. The controller connects the voice circuit
to line and, if appropriate, dials a remote telephone number.
