Note: Descriptions are shown in the official language in which they were submitted.
CA 02244636 2001-11-19
CD Quality Wireless Door Chime
BACKGROUND OF THE INVENTION
The present invention is directed toward the field of door chimes. In
particular, a door chime system that uses a high quality recorded sound to
indicate the
activation of a door chime button is disclosed. The invention provides the
distinct
advantage over the prior art of playing a CD quality recorded musical doorbell
indication sound instead of an artificial sound produced by an electronic
music
synthesizer chip.
The invention may be incorporated into any wireless door chime. United
States Patent No. 5,365,214, assigned to Dimango for example, discloses a door
chime having multiple detectors which transmit radio frequency ("RF") signals
to a
common receiver upon the depression of doorbell buttons. Each detectors is
associated with a specific doorbell button and includes means for allowing
manual
selection of a song or melody to be played by the receiver upon the receiver's
receipt
of the RF signal from the detector. The system allows different audible
indications to
be played in response to the depression of the doorbell button associated with
a
particular detector. As a result, a user can program each detector, such as a
front
doorbell detector and a back door detector, to signal, through its RF signal,
the
receiver to play a distinct audible indication whenever a specific doorbell
button is
pressed so that a user can determine from the audible indication played by the
receiver
which doorbell button was pressed.
A particular shortcoming of many of the wireless door chime systems, such as
the system described above, is the sound quality of the audible indication.
Typical
door chime systems produce a poor quality sound. Therefore, there remains a
need in
this art for a method of creating a high sound quality signal for use with
door chime
systems. There remain a more particular need for a method
CA 02244636 2001-11-19
2
of storing a CD quality sound into a door chime system. There also remains a
need for
a door chime system capable of playing a CD quality sound.
SUMMARY OF THE INVENTION
The present invention overcomes the problems noted above and satisfies the
needs in this field for a method and apparatus for recording a CD quality
digital sound
for use in a door chime system. In one embodiment the method of recording and
storing a CD quality sound for use in a door chime system includes the steps
of
providing a first sound, digitizing the first sound, filtering the digitized
sound signal,
converting the filtered digitized sound signal into a second sound, and
storing the
second sound into memory in the door chime system.
The present invention also provides a door chime system that is capable of
storing and playing a CD quality sound that has been recorded according to the
method disclosed herein. In one embodiment, a door chime system includes a
door
chime detector which sends a signals whenever it detects the activation of a
doorbell
button; a receiver which receives the signal from the door chime detector, the
receiver
including circuitry which outputs data sent from said door chime detector; a
code
detector having an input which receives data output from the receiver, the
code
detector determining whether a door chime sound is to be played as a result of
receiving the signal from the door chime detector, the code detector providing
a
command to play the high quality sound; a sound memory having an input which
receives a command from said code detector and outputs a signal representing a
high
quality sound upon receipt of said command; and sound producing means for
converting the high quality sound signals from the sound memory into an
audible
sound.
In another embodiment, the system includes wake-up circuitry for switching
the system from a sleep state to an active state.
According to an aspect of the present invention, there is provided a method of
storing a high quality sound for use in a door chime system comprising the
following
steps:
providing a recorded musical sound for use in the door chime system;
digitizing said musical sound wherein said digitizing step further comprising
the steps of
converting said recorded musical sound into an analog voltage signal;
CA 02244636 2001-11-19
2a
converting said analog signal into a digital signal; and
storing said digital signal in a computer file;
filtering said digitized sound, said filtering step further comprising the
steps
of:
applying a linear phase, low-pass-filter to said digitized sound signals; and
applying a rank order filter after applying said low-pass-filter;
converting said filtered digitized sound signal to a second musical sound
signal, said converting step further comprising the steps of
converting said filtered digitized sound signal to an analog signal;
converting said analog voltage signal to said second musical sound; and
recording said second musical sound on a recorder; and
storing said second musical sound into memory in the door chime system.
According to another aspect of the present invention, there is provided a
method of providing a high quality musical sound signal for use in a door
chime
1 S system, comprising the following steps:
providing a first musical sound signal;
digitizing said first sound signal;
filtering said digitized sound by applying a low-pass-filter to said digitized
sound signal;
filtering said digitized sound by applying a rank order filter to said low-
pass
filtered signal;
converting said filtered digitized sound signal to a second musical sound
signal; and
storing said second musical sound signal into memory in said door chime
system for providing the high quality musical sound signal to said door chime
system.
As will be appreciated, the invention is capable of other and different
embodiments, and its several details are capable of modifications in various
CA 02244636 1998-08-10
-3-
respect, all without departing from the spirit of the invention. Accordingly,
the
drawings and description of the preferred embodiment are to be regarded as
illustrative in nature and not restrictive.
BRIEF DESCRIPTION OF THE DRAWIN
The present invention satisfies the needs noted above as will become
apparent from the following description when read in conjunction with the
accompanying drawings wherein:
FIG. 1 is flow diagram of the method of storing a CD quality sound
according to the present invention.
Fig. 2 is a block diagram of a preferred embodiment of a chime receiver
according to the present invention.
Fig. 3 is a schematic diagram of a preferred embodiment of the code
detection, song memory, and sound producing portions of a preferred receiver
unit
according to the present invention.
Fig. 4 is a schematic diagram of a preferred embodiment of the RF receiver
and wake-up circuitry portions of a preferred receiver unit according to the
present invention.
2 0 DETAILED DESCRIPTION OF THE PREFE RFI~ EMBODLMFNT
Referring now to the drawings, Figure l sets forth a flow diagram of a
preferred method of storing a C'.D quality sound into the memory of a door
chime
receiver unit and figure 2 sets forth a block diagram of a preferred door
chime
receiver unit. In the preferred method, a digital audio tape (DAT) recording
of a
2 5 tune such as Tubular Bells or Westminster Chimes is made in the first step
of this
process, the Record Live Sound 1 step. Other known methods, however, may be
used such as the use of an analog audio tape recording or the use of live
audio.
In the second step, Digitize and place into a personal computer file 2, the
sound from step 1 is digitized, i.e., the sound is played and converted to an
analog
CA 02244636 1998-08-10
-4-
voltage representation of the sound and the analog voltage representation of
the
sound is converted, in turn, to a digital signal through an analog to digital
conversion. The digitized sound signal is then stored in a computer readable
data
file.
In the preferred method, this step 2 is performed using a sound card of a
personal computer. The sound card samples the recorded sound at a sampling
rate of 44 kHz and produces a digital representation of the recorded sound
which
it stores in a *.WAV file, commonly known as a wave file. This file format is
commonly used to store sounds for playback by a multimedia computer. This
initial sampling rate is not critical because the file will be re-sampled in a
later step
but, preferably, the rate is at least as high as the second sampling rate.
Next, in
the preferred method, the wave file is converted into an ASCII format sample
file
list. This step is not critical to the method, but allows a user to filter the
data
using a graphing program and allows the user to view the file with a text
editor.
The wave file format or any other file format, however, may also be edited and
will work satisfactorily for the purposes of this invention.
In the third step, Apply Low Pass Filter with Linear Phase 3, the
sound file created in step 2 is filtered using a linear low-pass-filter that
reduces the
bandwidth of the file but maintains the phase relationship between the
frequency
2 0 components. The preferred method utilizes a Bessel filter with a 3 kHz
cutoff
frequency.
The fourth step, Apply Rank Order Filter 4, utilizes a rank order filter, also
known as a median filter, to selectively eliminate any noise spikes from the
data
file. This filter sets each sample to the average or trend of the surrounding
2 5 samples. In the preferred method, the rank order filter had a five sample
window.
The combination of steps 3 and 4 combine to eliminate components of the sound
that could produce noise in the sound played by the door chime receiver such
as
high frequency components.
CA 02244636 1998-08-10
-5-
In the next step of the preferred method, Convert filtered file to an analog
tape recording 5, the data file from step 4 is converted back to a wave file
format,
the sound card is used to playback the sound, and the sound is recorded onto a
tape such as an analog tape or a DAT.
Finally, in the Transfer analog sound file into the chip memory 6
step, the recorded signal from step 5 is played and applied directly to the
sound
memory chip which samples the sound at an 8 Khz rate In the preferred
embodiment, an ISD 1420 from Integrated Storage Devices was used as the sound
memory chip although any type of sound memory chip could be used.
A preferred embodiment of a receiver unit from a wireless chime
unit that uses this invention will be described next. In the most basic
embodiment
of this invention, the wireless door chime receiver unit has a memory 11 that
stores one recorded sound for playback when a doorbell button is activated. A
further aspect ofthis invention allows the receiver unit to have a memory 11
that
stores a plurality of recorded sounds. In this latter case, either a
transnutter unit
or the receiver unit may provide means for selection of one of those
recordings.
The preferred embodiment of the receiver unit of this invention is
shown in block diagram form in Figure 2 and schematic form in Figures 3 and 4.
The transmitter unit (not shown) preferably, upon depression of a doorbell
button,
2 0 transmits a radio frequency signal that contains: ( 1 ) a wake-up signal,
(2) a house
code identifying the transmitter with a specific receiver, (3 ) a sound code,
which
indicates to the receiver which tune to play, and (4) a battery status bit,
which
indicates to the receiver the status of the transmitter battery.
The preferred Receiver unit, shown in block diagram form in
2 5 Figure 2, includes an RF receiver 7 for receiving the signal transmitted
by the
transmitter or doorbell detector (not shown), a Wake Up Circuit 8 which allows
most of the circuitry in the receiver unit to go into an inactive mode to
conserve
power and wakes up the circuitry when a signal from the doorbell detector is
received, a Code Detection Circuit 9 for decoding the code sent by the
doorbell
CA 02244636 1998-08-10
-6-
detector, a Low Battery Detect Circuit 10 for detecting and displaying to the
user
the status of both the doorbell detector battery and the doorbell receiver
battery,
a Song Memory 11 for storing the CD quality sound generated according to the
method of this invention and capable of storing multiple sounds, a Speaker
Driver
12 for amplifying the signal from the Song Memory 11, and a Speaker 13 for
playing the song selected from the Song Memory 11.
The preferred RF Receiver 7, shown in schematic form in Figure
4, receives AM modulated UHF signals from the Antenna 14 at P1 and produces
a low frequency representation of the modulation of the received signal. The
preferred RF Receiver 7 portion of the receiver unit consists of transistor Q2
and
transistor arrays and is shown in the schematic of Figure 4. The output of the
RF
Receiver 7 is provided at P4.
Wake Up Circuit 8, also shown on Figure 4, allows the Code
Detection Circuit 9 and the Song Memory 11 to remain in a low current "sleep"
state unless a valid signal is received by the RF Receiver 7. When a valid
signal
is received by RF Receiver 7, a SIN output signal from RF Receiver 7 is passed
to the SIN input of the Wake up Circuit 8. This wake-up signal, SIN, is
received
from the doorbell detector as an audio tone modulated on the RF carrier. This
tone is detected by phased-locked loop (PLL) U2 of Wake Up Circuit 8, shown
2 0 in Figure 4, which causes a Wake signal to be generated at P3 which
activates the
Code Detection Circuit 9 and the Song Memory 11 if the tone is present.
The Code Detection 9, shown schematically in Figure 3, compares
the house code in the received signal with the house code of the receiver unit
to
determine whether the signal is from a transmitter that is part of the same
system,
and, if so, decodes the sound code to determine which tune to play from Song
Memory 11. The decoding function of the Code Detection 9 is preferably
performed by microprocessor U3. The preferred microprocessor U3 is a
Microchip Corporation PIC 16C54. Microprocessor U3 receives data from the RF
Receiver 7 and compares the house code information stored within the data with
CA 02244636 1998-08-10
_7_
the house code which is set by the user by cutting the leads of diodes D7
through
D11 shown in Figure 3. An identical number of like diodes is provided in each
transmitter associated with the receiver. The preferred embodiment disclosed
provides up to 32 different house codes. Use of a different number of diodes
will
provide a different number of available house codes. Alternatively, DIP
switches,
jumpers, or other well known devices may be used to allaw the user to select a
house code.
Low Battery Detect 10 uses microprocessor U3 of Figure 3 to
decode the low battery bit of the received data. This bit is used to indicate
to the
receiver unit the status of the battery within the transmitter. In this
preferred
embodiment, a low battery detection circuit such as the one implemented by
transistors Q17 and Q18 of Figure 3 is used both in the receiver and the
transmitter to report the status of the battery in each respective'unit. The
Low
Battery Detect 10 also utilizes the circuit formed by transistors Q17 and Q18
to
verify the status of the receiver battery. Push-button switch S1 shown in
Figure
3 activates a low battery indicator using LEDs D4 and D5 shown in Figure 3 to
indicate the status of the transmitter and receiver batteries. When the user
presses
switch S1, the LEDs light if the corresponding battery is satisfactory. If a
low
battery was detected for either the transmitter or receiver, microprocessor U3
also
2 0 commands Song Memory 11 to play a beep at the end of the recorded tune. In
the
preferred embodiment, one beep indicates that the receiver battery is low; two
beeps indicates that the transmitter battery is low; and three beeps indicates
that
both batteries are low.
If microprocessor U3 of Code Detector 9 detects the correct house
2 5 code, then the microprocessor commands Song Memory 11 to play the
appropriate tune stored in memory. In the preferred embodiment, Song Memory
11 consists of sound memory chip U1, an ISD 1420, which contains the memory
and output drivers to produce differential analog sound signals directly at
pins 14
and 15 of the chip output.
CA 02244636 1998-08-10
-8-
The quad op amps U4 shown in Figure 3 provide low-pass-filtering
and convert the balanced output of sound memory chip U 1 to a single-ended
output needed to drive audio amplifier chip U5. The circuitry associated with
quad op amps U4 and audio amplifier chip U5 are conventional. The
microprocessor U3 can also disable the speaker using transistors Q1 and Q2
shown in Figure 3 when a tune is not being played to eliminate noise such as
that
caused when the microprocessor U3 is addressing the Song Memory 11.
Having described in detail the preferred embodiment and methods of the
present invention, including preferred modes of operation, it is to be
understood
that this operation and apparatus could be carried out with diil'erent
elements and
steps. This preferred embodiment is presented only by way of example and is
not
meant to limit the scope of the present invention which is defined and limited
only
by the following claims.
