U.S. patent application number 11/461047 was filed with the patent office on 2006-11-16 for vandal proof intercom system for apartment buildings.
This patent application is currently assigned to ELECTRONIC LOCKING SPECIALTIES. Invention is credited to John R. Pitzpatrick, John Unger.
Application Number | 20060256943 11/461047 |
Document ID | / |
Family ID | 32229358 |
Filed Date | 2006-11-16 |
United States Patent
Application |
20060256943 |
Kind Code |
A1 |
Unger; John ; et
al. |
November 16, 2006 |
VANDAL PROOF INTERCOM SYSTEM FOR APARTMENT BUILDINGS
Abstract
An electronic apartment station intercom unit, housed in a
vandal proof enclosure, providing a means for a tenant to
communicate with apartment building main entrance door panel and
means to unlock said door. This unit has a power storage unit that
enables this unit to be compatible with existing apartment building
switching units. This power storage unit can be in the form of
capacitors. In addition, this unit also contains a timer to shut
the intercom unit off after a preset period of time.
Inventors: |
Unger; John; (West Islip,
NY) ; Pitzpatrick; John R.; (Cold Spring Harbor,
NY) |
Correspondence
Address: |
WILLIAM COLLARD;COLLARD & ROE, P.C.
1077 NORTHERN BOULEVARD
ROSLYN
NY
11576
US
|
Assignee: |
ELECTRONIC LOCKING
SPECIALTIES
2043 WELLWOOD AVENUE
EAST FARMINGDALE
NY
|
Family ID: |
32229358 |
Appl. No.: |
11/461047 |
Filed: |
July 31, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10292060 |
Nov 12, 2002 |
7113578 |
|
|
11461047 |
Jul 31, 2006 |
|
|
|
Current U.S.
Class: |
379/167.01 |
Current CPC
Class: |
H04M 9/00 20130101; H04M
1/0291 20130101; H04M 1/18 20130101 |
Class at
Publication: |
379/167.01 |
International
Class: |
H04M 9/00 20060101
H04M009/00 |
Claims
1. An intercom system unit which interfaces with an intercom system
of a building the unit comprising: a) at least one energy storage
unit for the automatic detection of a potential when presented to
the interface; b) at least one energy storage device for the
temporary retention of the detected potential.
2-3. (canceled)
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation application of U.S.
patent application Ser. No. 10/292,060 filed on NOV. 12, 2002 and
titled VANDAL PROOF INTERCOM SYSTEM FOR APARTMENT BUILDINGS, the
disclosure of which is hereby incorporated herein by reference in
its entirety.
BACKGROUND
[0002] This invention relates to a vandal proof system for
installation in public/low cost housing where existing intercom
units are typically telephone handsets.
[0003] In such installations, landlords find intercoms costly,
lacking durability, and require routine maintenance. One of the
more significant problems encountered with telephone apartment
stations of the foregoing type has arisen from vandalism. With
increasing frequency, the handsets have been ripped off, the cords
cut, and the dials or buttons rendered inoperative such as by
inserting various instruments or a strong adhesive between the
moving parts of the apparatus. In some cases, the cover has been
pried loose and the interior components damaged or removed. These
problems have necessitated frequent monitoring and maintenance of
the individual stations which landlords are not able to
address.
[0004] The following references relating to intercom systems are
known in the art: U.S. Pat. No. 353,282 to Holm; U.S. Pat. No.
3,665,116 to Holstrom; U.S. Pat. No. 4,196,317 to Bartelink U.S.
Pat. No. 4,764,953 to Chern; and U.S. Pat. No. 5,966,432 to
Buckler.
[0005] In the past, some apartment switching units were installed
where apartment intercoms were furnished and maintained by the Bell
telephone company. Thus, many elements of apartment station
intercom units and apartment switching units functionally correlate
to telephone sets and a telephone network. Since the break-up of
Bell Telephone in 1983 into regional operating companies, (RBOCs),
responsibility for intercom maintenance has gradually fallen to
landlords. Now, landlords would prefer to replace these telephone
units with stand alone intercoms requiring minimal or no
maintenance, as well as being durable enough to withstand tenant
abuses and vandalism.
[0006] The interface between the system apartment station intercom
unit and the apartment building central intercom switch is similar
to a POTS system, wherein POTS is an acronym for a "plain old
telephone" system. This POTS system is essentially a twisted pair
with a 48 Volt open loop potential. In a phone system, when the
receiver is lifted (off hook), the local telephone set is engaged
or turned on, thus drawing power from the twisted pair. This off
hook condition signals the telephone central office, which then, in
turn supplies a dial tone. This process and system is called a loop
start system, and has been the basis of telephony for nearly a
century. Since the apartment station intercom unit interfaces with
a similar system, it is required to perform many of the same
functions as a telephone.
[0007] The apartment station intercom unit has a ring signal
detector and an electronic ringer. This ring signal detector alerts
a tenant that someone in the entrance has dialed his or her
apartment. To establish communication with the call, the tenant
presses the Push-To-Talk(PTT) button on the Apartment Station
Intercom Unit. This action does three things, first it signals the
apartment building central switch that the system or an apartment
station intercom unit is "off hook". In addition, it also enables
the transmit circuit and starts a timer.
[0008] When the tenant releases the PTT switch, he or she can hear
the caller. Once the tenant decides that the caller may enter the
building, the door release button is pressed, signaling the
apartment building central switch to release the door lock. This is
a the Bell Standard Dual Tone Multi-Frequency(DTMF) signal.
[0009] The timer that was initiated when the tenant first pressed
the PTT button, and prevents the tenant from engaging the caller in
a prolonged conversation, which is considered an abuse of the
system.
SUMMARY
[0010] Therefore, an object of the invention, is to provide a more
suitable instrument for use in public and low cost housing.
[0011] More specifically, it is an object of this invention to
provide an Apartment Station Intercom Unit, which is highly
resistant to vandalism, very reliable and low in cost.
[0012] Another object of the invention is to provide a
communications station of the character indicated in which the
buttons or other moving portions of the apparatus can not be
rendered inoperative through the use of various instruments, such
as adhesive.
[0013] It is further an object of the invention to prevent tenants
and callers from engaging in lengthy conversation.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] Other objects and features of the present invention will
become apparent from the following detailed description considered
in connection with the accompanying drawings which disclose at
least one embodiment of the present invention. It should be
understood, however, that the drawings are designed for the purpose
of illustration only and not as a definition of the limits of the
invention.
[0015] In the drawings, wherein similar reference characters denote
similar elements throughout the several views:
[0016] FIG. 1A is a front view of the system known as an apartment
station intercom unit;
[0017] FIG. 1B is a side view of the system shown in FIG. 1A;
[0018] FIG. 2 is an electrical schematic circuit diagram of the
system shown in FIG. 1A;
[0019] FIG. 3 is a system block diagram of the system as it is
coupled to other electronic devices in a building;
[0020] FIG. 4 is a cross sectional view taken thru line I-I of FIG.
1, showing tamper resistant screw fastener, which is used to secure
the apartment station intercom unit to wall mounting bracket;
[0021] FIG. 5 is a perspective view of a tamper resistant
screw;
[0022] FIG. 6 is a large side cross sectional view shown in FIG.
4;
[0023] FIG. 7A is a front view of a wall mounted plate shown in
FIG. 4;
[0024] FIG. 7B is a top cross-sectional view of the wall mounted
plate shown in FIG. 7A; and
[0025] FIG. 8 is a front view of a back plate shown in FIG. 4.
DETAILED DESCRIPTION
[0026] Referring in detail to the drawings, FIG. 1A shows an
external view of system 100 according to the invention. System 100
is intended for use in apartment buildings with a signal entrance.
Not shown are models for building with a plurality of entrances.
These differences are defined by the number of door release
buttons.
[0027] System 100 has a push to talk button or PTT 7, and a door
release button 19 that are shown accessible to a user. There is
also shown a tamper proof screw 105 which fits through hole 105',
which is used to secure face plate 103 to a back wall. FIG. 1B
shows a side view of system 100 which also shows door release
button 19 and tamper proof screw 105 secured into housing 103.
[0028] FIG. 2 is an electrical schematic diagram of system 100
shown in FIG. 1A. To alter system 100 to be coupled to almost any
power supply including a telephone line, it contains a plurality of
filter capacitors 12 and 28 that are of a sufficiently high value
as to hold an adequately long charge during this period of use.
[0029] When the system receives a ring signal from the apartment
building intercom after button 7 is depressed in system 32 as shown
in FIG. 3, a ring detector 8 will detect a level between 120-280
volts peak to peak at a frequency of between 15 to 30 Hertz,
measured at conductors 22a and 22b of FIG. 2. Ring detector 8 then
causes ringer or bell 9 to emit an audible tone. This tone is in
the frequency range of 400 to 2,000 Hz with a minimum amplitude of
80 dB.sub.SPL measured at a distance of 18 inches from the
apartment station intercom unit 100.
[0030] While ringer 9 is enabled, a DC voltage, equal to the peak
voltage on 22a and 22b, flows from bridge rectifier 2, across line
53. This causes a current to flow through resistors 25 and diode
26, charging capacitor 28 to a voltage equal to the zener breakdown
voltage of diode 27 at line 46.
[0031] Line 46 becomes the supply voltage to a hook switch latch
and time-out circuit 5. The values selected for resistor 25 and
capacitor 28 allow sufficient energy transfer on the first half
cycle of the ring signal to place hook switch latch and time-out
circuit 5 in operational mode. During this power-up, a capacitor 44
stores the power on a reset line 45, below its threshold voltage
for a sufficient period to allow hook switch latch and time out
circuit 5 to start in the proper state. In this state, lines 42 and
50 are held at logic "0", while line 52 is held at a logic "1".
[0032] With line 50 held "low", the electronic "hook switch",
consisting of resistors 47 and 49 and MOSFETs 3, and 4, is held in
the "on hook" or open circuit state. In this state, the gate
voltage of the N-channel MOSFET 4 is below its threshold voltage.
Therefore, the drain current of MOSFET 4 is 0. This results in a
zero current flow in resistors 47 and 49. With no current in
resistor 49, the gate-drain voltage of the P-Channel MOSFET 3 is
zero. Therefore, MOSFET 3 has zero drain to source current flow,
and the remaining circuits are not activated.
[0033] When the user elects to respond to a ringing apartment
station intercom unit or system 100, he presses push to talk (PTT)
switch 7. Upon doing so, line 52 is set to ground potential through
the closed PTT switch 7. This sets hook switch latch and timer-out
circuit 5. This action releases a clamping circuit internal to hook
switch latch and time-out circuit 5, and connected line 42,
allowing capacitor 41 to start charging by the current supplied
through resistor 40. Also, line 50 is set "high" forcing the MOSFET
4 to saturate. This causes current to flow through resistors 47 and
48 that in turn, turns on MOSFET 3.
[0034] Once MOSFET 3 is on, current will flow through inductor 11
charging capacitor 12 and forming a DC voltage supply to amplifiers
13 and 10, DTMF generator 18 and all other circuits requiring DC
power. Since line 54 contains both an audio signal and DC power, it
is important that line 54 have a high AC impedance. Inductor 11 and
filter capacitor 12 form the DC power source for the intercom. This
combination is the classic L-C filter for power supplies. Line 54
has a high AC impedance node, while line 29 has a low AC
impedance.
[0035] While PTT switch 7 is depressed, and line 52 is grounded,
the gate of MOSFET 6 is also grounded to turn the device off. This
condition allows line 61 to go high, thus disabling speaker
amplifier 13. With line 61 high (or at a Vcc, the potential of line
29) NPN transistor 16 is saturated when current flows thru resistor
62. Transistor 16 is a high gain device therefore, and the voltage
drop through resistors 60 and 62 due to the base current is
negligible in this application. When transistor 16 is saturated,
the collector to emitter current flow supplies a bias current to
emitter follower 17, and electret microphone 15. In the transducer
of electret microphone 15, a vibrating diaphragm constitutes one
plate of a capacitor, while the charge stored on the capacitor
varies in response to fluctuations in sound impinging upon the
diaphragm. This varying stored charge appears as voltage variations
(referenced to ground) at line 64, in the microphone's output.
[0036] The user, while holding down PTT switch 7 may talk to the
caller at the apartment building lobby entrance. The audio from
microphone 15 carried by line 64 to the base of emitter follower
17. The signal is carried from emitter follower 17 to microphone
amplifier 10 through capacitor 66 and resistor 67. The output of
amplifier 10 is coupled to line 54 through capacitor 56 and
resistor 55. With the proper component selection, the microphone
circuitry delivers a -14 dBm to 0 dBm signal to lines 22a and 22b
through MOSFET 3 and diode bridge 2, for a 75 dB.sub.SPL acoustic
source when measured 18 inches from the front of the apartment
station intercom unit 100. The frequency response of the microphone
circuit is .+-0.3 dB in the frequency range of 300 Hz to 3300 Hz, a
standard in the telephone industry.
[0037] When the user releases PTT switch 7, the voltage in line 52
rises to the potential on line 29 through resistor 51. This
condition forces MOSFET 6 to turn on, pulling the potential on 61
low. This condition enables speaker amplifier 13, and turns off
transistor 16, thereby disabling microphone 15. The user can now
listen to the caller located in the apartment building lobby
entrance.
[0038] It should now be apparent that this circuit represents a
half duplex communication link. This communication link is defined
as one where the transmit and receive functions are mutually
exclusive. It should also be apparent that a user of the Apartment
station intercom unit 100 cannot initiate communications since
there is no power present in the unit while idle.
[0039] The user has a communication link until the hook switch
latch and timer circuit has not timed out. Typically, the time out
is set for one minute. This occurs when the voltage at point 42
reaches 66% of the value at line 29. Once this happens, the voltage
in line 50 decreases, disabling the electronic hook switch. This
opens the circuit at lines 22a and 22b, and this circuit opening is
sensed by apartment building intercom system 32 as a disconnect or
on hook condition.
[0040] When the circuit times out, the current in line 54 rapidly
falls to zero, and the collapsing magnetic field in inductor 11
tries to force the potential negative on line 54. To prevent damage
to MOSFET 3, diode 59 shunts the resulting negative flow to
ground.
[0041] If the user decides to allow entry to the caller, and the
system has not timed out, he may press door release button 19 or
20. This action enables the DTMF generator 18 to send a DTMF 9 or a
DTMF 5 signal to the apartment building intercom system 32 of FIG.
3. These two numbers are the primary standard for signaling a door
release in apartment complexes. However, any DTMF tone can be used.
Once the apartment building intercom system 32 receives this
signal, it will release the electric door lock 35.
[0042] An over voltage device 1 is placed across conductors 22a and
22b. Over voltage device 1 may be of conventional construction, and
comprises a pair of semi conductive components that "breakdown"
under an over voltage condition. Usually the arrangement is such
that one over voltage device 1 protects against over voltages of
one polarity, while another over voltage device 1 is arranged to
protect against over voltages of the opposite polarity. Another
suitable device is a voltage dependent resistor which has a
resistive value that decreases rapidly when an over voltage
condition exists.
[0043] A diode bridge or ring bridge 21, comprising 4 diodes is
inserted between the apartment station intercom unit interface,
conductors 22a and 22b, ring detector 8 and ringer 9. Bridge 21
insures that the proper polarity of the DC voltage to the ring
detector is maintained regardless of the polarity of 22a and 22b.
Thus, apartment station intercom unit 100 is protected from reverse
polarity even if the wiring 34, which includes lines 22a and 22b
from 33 to 30 as shown in FIG. 3 have been inadvertently reversed
upon installation.
[0044] FIG. 4 shows a cross sectional view of the device shown in
FIG. 1A taken through the line I-I. FIG. 4 essentially shows how
device 100 including wall plate 103 that can be secured to a wall
such that this device becomes tamper proof. This embodiment is
equipped with tamper proof screws 105 and 106 (See FIG. 5). FIG. 5
shows a pin and hex screw, which has a head 122, a hex shape 124
and a pin 126 extending inside of the hex shape. This type screw is
disclosed in U.S. Pat. No. 5,497,533 to Karlsen issued on Mar. 12,
1996 incorporated herein by reference. Thus, no ordinary wrench can
be used to turn these screws. Instead a particular hex wrench that
has a central aperture to accommodate the pin is required. While it
is not impossible to remove tamper resistant screws, it is an
arduous task to do so without a special tool. This special hex
wrench, is one having a central aperture, and must be used to
provide clearance from a blocking pin that aligned with the axis of
screw 105 and within the hex aperture and wherein this hex wrench
extends the length of the aperture. Screw 106 is located concentric
with screw 105 and is of the same type. Thus, to turn screw 106 one
must first remove screw 105. If someone is successful in removing
screw 105, it is a much more difficult task to remove screw 106.
Screw 106, when tightened, locks into bushing 107 and drives into
wall mounted plate or bracket 103 thereby locking the apartment
station intercom unit housing including cover or front plate 101 to
the wall mounting plate 103. In addition screw 105 screws into
bushing 104 to clamp cover plate 101 to an intermediate plate 108.
Also shown in this drawing are the speaker 14 and microphone
15.
[0045] FIG. 6 shows a full side cross sectional view as shown in
FIG. 4. In this view, there is wall-mounted bracket 103 that is
coupled to a wall, back plate 102 which couples to wall mounted
bracket 103, intermediate plate 108 which can be coupled to a front
plate 101. There is also shown spacers 109 and 110 for spacing a
circuit board 115 away from back plate 102. Additional spacers 113
and 114 are used to space circuit board 115 away from intermediate
plate 108.
[0046] FIG. 7A shows a front view of wall-mounted bracket 103 while
FIG. 7B shows a top cross-sectional view of this bracket. Wall
mounted bracket 103 has side-walls 103' which are covered by cover
plate 101 when cover plate 101 is clamped down on wall mounted
bracket 103. As shown in FIG. 6, side walls of cover plate 101
cover side walls 103' to form a tight cover. This tight cover makes
the unit more vandal proof because a vandal would most likely not
be able to fit a screwdriver or other prying device between the
intersection of side walls 103' and the side walls on cover plate
101. In addition, FIG. 7A shows heads 111 and 112, which can be
screw heads or formed integral with wall mounted bracket 103 and
can be used to clip an additional plate to wall-mounted bracket
103.
[0047] FIG. 8 shows a front view of the back plate 102 which
contains a securing hole 114 which is used to secure over heads 111
or 112. There is also another securing hole (not shown) disposd
opposite securing hole 114 which allows back plate 102 to secure
onto wall mounted bracket 103.
[0048] To install system 100, it first comes pre assembled with
cover plate 101 coupled to back plate 102 with all the necessary
electronic components disposed inside. Back plate 103 is next
secured on a wall, separate from the system. Back plate 103 is
secured by any known means such as via screws. Next, hole 114 and
an opposite spaced hole (not shown) is secured over heads 111 and
112 on back plate 103. Next, screw 106 is fed through hole 105'
(See FIG. 1A) in cover plate 101 and tightened to secure back plate
102 to wall mounted plate 103 and thus to a wall. Next, screw 105
is fed through the same hole 105' to further secure cover plate 101
to intermediate plate 108 so that cover plate 101 has protection
from being removed from system 100. Thus, to remove system 100 from
a wall, both screws 105 and 106 would have to be removed.
[0049] While the embodiment illustrated in the drawings and
described above is for and intercom system designed to unlock a
single door, it should now be apparent to those skilled in the art
that the subject invention can be designed to unlock a plurality of
doors. It is preferred, therefore, that the present invention
extend to cover those modifications.
[0050] Though there are many similarities with telephony, there are
significant differences. Since being dropped from the telephone
network, many vendors have introduced their own interpretations of
the Bell Standard. One method is where no voltage is applied to TIP
and Ring during non use, contrary to the 48 VDC that is always
present on phone lines. Another is the lack of zero voltage
crossing circuitry in their ring signal generators. This gives the
system a ring signal that can start and stop at any point in the
ring cycle. The result is extremely high voltage slew rates or
transient voltages (dv/dt) that are harmful to electronic circuits
not properly protected. The last significant difference is that the
48 VDC component appears 150 milliseconds after the ring signal has
ceased. This is problematic when initializing intercom circuitry,
since this appears to such circuitry as a disconnect. Thus,
capacitors 12 and 28 are introduced into the system to control the
flow of power, and to store power in the system.
[0051] Accordingly, while at least one embodiment of the present
invention has been shown and described, it is to be understood that
many changes and modifications may be made thereunto without
departing from the spirit and scope of the invention as defined in
the appended claims.
* * * * *