Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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This invention relates to a system for alerting a
telephone user who cannot hear the telephone ringing, that the
telephone should be answered.
Quite often, and for a variety of reasons, a ringing
telephone will not be heard. The telephone user may be deaf. The bell
volume may be deliberately turned down, perhaps in consideration of
someone else sleeping on the premises. There may be the noise of a
vacuum cleaner, radio, television or gramaphone record which drowns the
sound of the ringing telephone. Lastly, the telephone user may be in
the garden or garaqe or otherwise remote from the telephone set and so
too far away to hear the ringing.
In such circumstances, a system for alterting the
telephone user would be convenient.
According to the invention, there is provided a system
for altertinq a telephone user when the telephone is being energized by
rinqing voltage, the devtce comprising a telephone unit including a
transmitter having an output which is controlled by ringing voltage on
the telephone line, and a user unit including a receiver for receiving
a signal from the transmitter, and a transducer under the control of
the receiver for convertinq the received signal into a signal which is
non-audibly sensible by the telephone user.
Preferably, the transducer is actuated to produce a
physical vibration. The transducer can be mounted within a housing
worn by the telephone user whereby to give a tactile response. The
housing can, for example, be wrist worn. The user unit preferably
includes a detector to detect a predetermined frequency of signal
received by the receiver, the detector operably coupled to a low-power
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hattery-driven motor circuit. The transmitter is preferably mains
driven, ringinq voltage from the telephone line being applied to the
transmitter through an optical isolator whereby to prevent mains
voltaqe and system noise from appearing on the telephone line.
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 schematic diagram of an alertingsystem accordinq to the invention;
Figure 2 is a detailed circuit representation of a
transmitter unit forming part of the system of Figure 1;
Figure 3 is a detailed circuit representation of a
receiver unit forming part of the system of Figure 1; and
Figure 4 shows a wrist mounted housing for the Figure 3
circuit.
Referrinq in detail to the block schematic diagram of
Figure 1, there is shown a telephone tactile alert system. Ringing
voltage from a telephone line 10 is applied both to a telephone set 12,
and, through an optical isolator 14, to a pulse generator 16 which
controls the output of a radio transmitter 18. While ringing voltage
is present on the telephone line, the transmitter 18 emits a radio
frequency signal which is picked up by a receiver 20. A detector 22
~ monitors the received signal and, in response to a selected frequency
; component above a pre-set threshold level, actuates a transducer 24
which converts the received signal to a physical vibration. The
vibration elicits a tactile response in a user wearing the receiver
unit.
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Referring now to Figure 2, the transmitter unit has a
plun 26, which mates with one socket of a standard double socket wall
mounted ~junction unit which is connected to the telephone line. The
other socket is engaqed hy a plug electrically connected to the
telephone set.
A 0.7 V output generated at a voltage tap 34 is directed
to the optical isolator 14 when ringing voltage is present. The
voltage tap includes a capacitor 3fi to prevent oPeration in response to
nc and low voltaqe signals. A zener diode 40 conducts when ringing
n voltaqe (8nv RMS), is present; a further diode 42 is incorporated for
protection.
The optical isolator is a standard unit incorporating a
linht emitting diode and a PIN photodiode. The output from the optical
isolator is taken to a timer 44 (IC7555), which produces DC pulses with
a 4 second-2 second mark-space duty cycle, pulse initiation
correspondin~ to the start of ringing voltage pulses. DC power
generated in network 28 is derived from mains AC.
The output from the timer 44 is directed to the base of a
transistor n1 forming the first stage of a multi-stage transmitter
2n amplifier 48. The amplifier output enables a local oscillator circuit
51 which generates a carrier siqnal at a crystal controlled frequency
of 53.1 MHz. The keyed carrier signal is directed to a short wire
antenna 32 through a filter circuit 52.
Referring in detail to Figure 3, the receiver includes a
crystal controlled local oscillator 54 at a frequency of 53.55 MHz. At
a mixing circuit 56 the locally qenerated frequency is mixed with the
incominq carrier frequency to generate an intermediate frequency of
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~sn KHz. The intermediate frequency signal is amplified at a
multi-staqe amplifier 58, the output from which is rectified at
transistor Q5. The nc output is taken to a threshold detection network
includinq a low-power consuming VMOS switch 60. The switch, when
actuated, directs current to a micromotor 62. One example of a
suitahle motor which operates from a nominal supply of 1~ V and draws
ahout 3n mA current can be obtained from ESCAP Inc. under the
specification No. 712 L81 10S. An output shaft of the micromotor 62 is
fitted with an eccentric weight (not shown) which causes the motor body
to vibrate when the motor is energized. The network 64 functions
essentially as a voltage regulator. A 6 V battery supply 66 supplies
power to the receiver and detector.
Referring to Figure 4, the motor and the 1~ V battery are
taped toqether and friction fitted into one compartment 72 of a moulded
plastic bracelet 71. A tactile sensation is induced in the wearer's
wrist by vibration of the motor body against a compartment wall. The 6
V battery together with the receiver and detector circuits are housed
within a second compartment 76 of the bracelet. The bracelet has a web
portion 78 offering rudimentary flexibility, the web portion extending
hetween the compartments 72 and 76. Covers 80 adapted to close the
compartments can be press fitted against the moulded bracelet, the
covers and the moulding having cooperating ribs and recesses (not
shown). Attached to lugs 82 formed at each of the compartments 72 and
76 are Velcro (Registered Trademark) strips 84 by means of which the
bracelet incorporatinq the receiver unit can be secured around the
user's wrist.
As previously indicated, in operation the ringing voltage
actuates both the telephone set bell and the radio transmitter to emit
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radio frequency hursts corresponding approximately in length to the
lenqth of rinqinq voltaqe bursts. If a switch S1 shown in Figures 3
and 4 is placed in the "Orl" position, then the receiver unit receives
the radio si~nal and produces corresponding vibration of the micromotor
aqainst the wall of the bracelet. This produces a tactile response in
the user who is thereby alerted that the telephone must be answered.
Upon pickinq up the telephone handset, rinqing voltage ceases as does
vibration of the micromotor 62.
Althouqh the invention has been described in terms of a
radio signal transmitted from a transmitter unit located adjacent to
the telephone set, the transmitter output being modulated by ringing
voltage, other tvpes of transmitter and receiver could be used. Thus
the transmitter and receiver could alternatively be incorporated in an
electroma~netic induction loop. As a further alternative, the
transmitter and receiver could operate on the basis of infrared
transmission.
