US007530091B2
(12) Ulllted States Patent
(10) Patent N0.:
Vaughan
(45) Date of Patent:
(54)
VOIP DROP AMPLIFIER
(75)
Inventor;
Jay Vaughan, G?bens AZ (Us)
(Continued)
(Us)
Notice:
FOREIGN PATENT DOCUMENTS
Subject to any disclaimer, the term of this
patent is extended or adjusted under 35
JP
200430483
U.S.C. 154(b) by 669 days.
(22)
OTHER PUBLICATIONS
_
“Clipcomm CP-100P,” VOIPSupply.c0m http://wwwvoipsupply.
Flled'
Jul‘ 18’ 2005
(65)
com/productiinfo.php?pr0ductsiid:305, 2 pages printed from
Prior Publication Data
US 2006/0015921A1
Internet Jun’ 6’ 2005'
Jan. 19, 2006
_
(60)
(Commued)
_
Primary ExamineriChristopher Kelley
Related U-s- APPheatmn Data
Provisional application No. 60/589,337, ?led on Jul.
19, 2004.
(51)
Int. Cl.
(52)
H04N 7/173
(2006.01)
H04] 1/02
(2006.01)
us. Cl. ..................... .. 725/106; 725/127; 725/126;
(58)
3/2004
(Continued)
(21) Appl. No.: 11/182,738
.
May 5, 2009
6,671,253 B1
12/2003 Alexander, Jr. et al.
6,690,789 B1
2/2004 Hamilton
6,735,302 B1 * 5/2004 Caine et al. ............... .. 379/405
(73) Assignee: PCT International, Inc., Gilbert, AZ
(*)
US 7,530,091 B2
Assistant ExamineriFranklin S Andramuno
(74) Attorney! Agent! 0'’ FirmiRlchard C- Lltman
(57)
ABSTRACT
The VOIP drop ampli?er connects end user equipment to a
broadband system, such as that provided by a cable provider.
The ampli?er includes a Splitter for Connecting the Cable
725/105; 370/493
signal to multiple output connectors, and RF ampli?ers com
Field of Classi?cation Search ............... .. 725/106,
Pensating for losses in the Splitter and other Passive Compo
725/105’ 126’ 127; 370/493
See application ?le for Complete Search history
nents in the ampli?er. The drop ampli?er includes an input
connection for accepting a broadband cable signal from a
cable system and returning broadband signals to the cable
system. The drop ampli?er includes an ampli?cation path
connecting the input connection to the plurality of output
connections through RF ampli?ers and a splitter, and a bypass
path that bypass the splitter and forward and reverse ampli?
(56)
References Cited
U.S. PATENT DOCUMENTS
5,016,244
5,696,895
6,075,784
6,175,565
6,202,169
6,373,817
6,477,197
6,640,239
A
A
A
B1
B1
B1
B1
B1
5/1991
12/1997
6/2000
1/2001
3/2001
4/2002
11/2002
10/2003
Massey, Jr. et al.
Hemphill et al.
ers in the ampli?cation path to connect the input connection
directly to the output connection for the essential circuits. A
Frankel et al.
McKinnon et al.
sensing circuit monitors the ampli?ers and the supply volt
RaZZaghe-Ashra? et al.
Kung et al.
ages, and selects the bypass path When a failure is detected.
Unger
6 Claims, 5 Drawing Sheets
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US 7,530,091 B2
Page 2
U.S. PATENT DOCUMENTS
8/2004 Dan et a1.
6,785,907 B1
1/2005 Daruwalla et a1.
6,839,829 B1
2002/0101817 A1
8/2002 TeiXeira
2002/0101818 A1
8/2002 TeiXeira
2003/0066082 A1 * 4/2003 Kliger et a1. ................ .. 725/80
2003/0214939 A1
11/2003 Eldumiati et a1.
2004/0027992 A1
2/2004 Volkening et 31.
2004/0170160 A1 * 9/2004 Li et a1. .................... .. 370/352
2005/0169056 A1 * 8/2005 Berkman et a1. ..... .. 365/185.22
OTHER PUBLICATIONS
“VOIP/PSTN 2-Line Intelligent Switch (GateWay/Ph0ne/ATA),”
eBay.c0m
http://cgi.ebay.c0m/Ws/eBayISAPI.dll?VieWItem
&item:5193203853&categ0ry:11188, 7 pages printed from
Internet on Jun. 6, 2005.
“Epygi Quadro 16X #16209,” The VOIPConnectioncom http://WWW.
thevoipconnection.com/store/customer/product.php
?pr0ductid:16209&cat:25 5&page: 1, 2 pages printed from Internet
on Jun. 6, 2005.
FOREIGN PATENT DOCUMENTS
JP
2005-5875
1/2005
* cited by examiner
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1
2
VOIP DROP AMPLIFIER
80,483, published Mar. 11, 2004, Which shoWs in FIG. 1 a
VoIP adapter for telephone communications that sWitches
CROSS REFERENCE TO RELATED
APPLICATION
from a telephone line netWork, such as a packet sWitched
telephone netWork, to a VoIP netWork to maintain communi
cations When a failure in the telephone line netWork is
This application claims the bene?t of US. Provisional
Patent Application Ser. No. 60/589,337, ?led Jul. 19, 2004.
detected. Another representative device is shoWn in Japanese
Patent No. 2005-5,875, published Jan. 6, 2005, Which also
BACKGROUND OF THE INVENTION
shoWs in FIG. 1 a device for sWitching from a telephone line
netWork, such as a packet sWitched telephone netWork, to a
VoIP netWork to maintain communications When a failure in
1. Field of the Invention
The present invention relates to cable television systems,
the poWer supply for the telephone line netWork is detected.
While the above-mentioned patent references describe cir
cuit monitoring and sWitching to maintain telephone commu
nications, neither describes maintaining VoIP communica
tions despite failure of components in an IP netWork
providing the VoIP infrastructure.
None of the above inventions and patents, taken either
and particularly to splitter/ampli?er systems for delivering
diverse communication services, including voice over IP
(VoIP) telephone services.
2. Description of the Related Art
Cable television operators provide a variety of diverse ser
vices to consumers. These services include high speed Inter
net access, video on demand, pay-per-vieW services, andVoIP
services. Cable operators provide these services multiplexed
singly or in combination, is seen to describe the instant inven
20
over a single cable using such techniques as frequency divi
sion multiplexing (FDM). These services are characterized
by the need to provide forWard and reverse communication
path. The forWard path is used to transmit data to the user,
While the reverse path is used to return data to the cable
operator. The return data might include orders for video on
demand or pay-per-vieW content or data transmitted by the
SUMMARY OF THE INVENTION
25
Key components of CATV systems are drop ampli?ers.
30
system and returning broadband signals to the cable system.
the input connection to a plurality of output connections
35
40
at the cable operators system, and a reverse ampli?er for
reverse path ampli?er is required. For example, set top boxes
45
Among the services provided by the cable provider, it is
The sWitching circuit is controlled by a dc current and voltage
sensing circuit.
particularly important that the voice over IP (VoIP) service be
The dc current and voltage sensing circuit monitors dc
reliable. While such services as video on demand or pay-per
50
used to provide telephone communications. Telephone com
munication are vieWed as vital services, particularly during
situations involving medical emergencies or natural disasters
Where communications may be necessary to make essential
voltage supplied to the ampli?er circuitry. The sensing cir
cuitry also monitors the current supplied to the forWard and
reverse ampli?ers, or to the forWard ampli?er alone When the
reverse ampli?er is not provided in the ampli?cation path.
The dc voltage supplied to the VoIP circuitry is compared to
55
or doWned poWer lines. The VoIP circuits may be vieWed as
a reference value to determine Whether the dc voltage is
suf?cient to operate the VoIP active components. When the dc
voltage is insuf?cient the dc current and voltage sensing
circuit operates the sWitching circuit to select the bypass path.
essential services because of the need to maintain the circuits
in emergency situations.
Because the ampli?ers used in the systems are active com
ponents employing complex circuitry and requiring electrical
The VoIP ampli?er further includes a sWitch circuit for
selecting betWeen the ampli?cation path and the bypass path.
the reverse path ampli?er unnecessary.
reports, such as injuries, life threatening medical conditions,
through ampli?ers and a splitter, and a bypass path that
bypasses the splitter and the forWard and reverse ampli?ers in
the ampli?cation path to connect the input connection
directly to the output connection for VoIP. A sensing circuit
monitors the ampli?ers and the supply voltages and selects
the bypass path When a failure is detected.
The ampli?cation path includes a forWard ampli?er for
amplifying the forWard signals, Which are signals originating
amplifying the reverse signals, Which are those signals origi
nating at the end user’s equipment.
level in the reverse path may be suf?ciently high so that no
vieW are vieWed as luxury or non-essential services, VoIP is
nection for accepting a broadband cable signal from a cable
The drop ampli?er includes an ampli?cation path connecting
Ward and return signal into separate components for ampli?
cation using separate ampli?ers. In some cases the signal
and cable modems typical provide high output levels, making
The VoIP drop ampli?er connects end user equipment to a
broadband system, such as that provided by a cable provider.
The ampli?er includes a splitter for connecting the equipment
to multiple output connectors, and RF ampli?ers compensat
ing for losses in the splitter and other passive components in
the drop ampli?er. The drop ampli?er includes an input con
user for destinations on the Internet.
These ampli?ers are inserted into the cable transmission path
to make up for losses in the transmission system. Signals are
weakened as they pass through cables and components, such
as splitters. Splitters are used to separate the services pro
vided by the cable operator for distribution to the appropriate
customer equipment for receiving the service.
Typically the return signal operates at a comparatively
loWer frequency than the forWard path. For example, in a
typical system the return signal is in a bandWidth of 5 MHZ to
about 40 MHZ, While the forWard path operates at 50-1000
MHZ. Diplex ?lters are used to separate the combined for
tion as claimed. Thus, a VOIP drop ampli?er solving the
aforementioned problems is desired.
The ampli?er current is compared to tWo reference values
60
poWer to operate, the drop ampli?ers are potential failure
to determine Whether the current is Within a range including a
loWer and an upper current limit. When the ampli?er current
points for VoIP services. In some situations, an emergency or
is outside this range, Which corresponds to the normal range
disaster that requires the use of the VoIP services also results
of expected ampli?er currents, the dc current and voltage
circuit operates the sWitching circuit to select the bypass path.
in a loss of electrical poWer, disabling the drop ampli?ers and
interrupting vital VoIP communications.
Several devices have been developed for VoIP systems. A
representative device is shoWn in Japanese Patent No. 2004
65
Under normal voltage and current conditions, the dc cur
rent and voltage sensing circuit controls the sWitching cir
cuitry to select the ampli?cation path. The bypass path sup
US 7,530,091 B2
4
3
plies only the VoIP output or other output connections
The VoIP connector 38 is connected via a cable to a second
designated as essential, While the ampli?cation path supplies
cable modem 32, Which is connected to a multimedia terminal
adapter (MTA) 34. The MTA is connected to one or more
all of the output connections including the essential and non
essential connections. In a typical case, only the VoIP output
is designated as essential.
The forward and reverse ampli?ers may provide suf?cient
VoIP telephones 36. The remaining output connectors 40e
40g are shoWn as unused, but may be connected to additional
devices. For example, an additional cable modem and MTA
may be connected to one of the unused connectors to provide
additional VoIP telephone service, or a third cable modem for
Internet access may be connected to one of the unused output
gain to compensate for losses in VoIP drop ampli?er. Alter
natively, these ampli?ers may provide additional gain to com
pensate for losses elseWhere in the cable system, such as
losses in the cable connecting the VoIP to the cable operator’ s
connectors.
system.
The VoIP drop ampli?er 20 is shoWn poWered by an unin
These and other features of the present invention Will
terruptible poWer supply (UPS) 22, Which provides poWer to
become readily apparent upon further revieW of the folloWing
the VoIP drop ampli?er 20 via the input connector 42. Alter
natively, poWer may be provided to the VoIP drop ampli?er 20
speci?cation and draWings.
from a simple Wall transformer.
FIGS. 2 and 3 are block diagrams by Which the basic
BRIEF DESCRIPTION OF THE DRAWINGS
operating principles of the VoIP drop ampli?er 20 may be
FIG. 1 is a block diagram of a typical CATV system incor
porating a VOIP drop ampli?er according to the present
invention.
FIG. 2 is a functional block diagram of the VoIP drop
20
understood. FIG. 2 shoWs the ampli?er in the normal condi
tion, While FIG. 3 shoWs the ampli?er in a bypass condition.
As shoWn in FIG. 2, the RF signal to and from the cable
system is routed through the input connector 44 to a ?rst
ampli?er according to the present invention operating under
normal operating conditions.
bypass sWitch 52. A sWitch circuit comprises this ?rst bypass
FIG. 3 is a functional block diagram of the VoIP drop
ampli?er according to the present invention sWitched to the
bypass operating condition after detecting a fault in the sys
beloW. The sWitch circuit is controlled by dc current and
sWitch 52, as Well as a second bypass sWitch 54 described
25
tem.
FIG. 4 is a simpli?ed schematic diagram of an embodiment
of current and voltage sensing circuitry that may be used in
the VoIP drop ampli?er according to the present invention.
30
FIG. 5 is a simpli?ed schematic diagram of an embodiment
of a VoIP drop ampli?er according to the present invention
using relays as the bypass sWitches.
Similar reference characters denote corresponding fea
tures consistently throughout the attached draWings.
voltage sensing circuitry 66. When the dc current and voltage
sensing circuitry 66 detects that the ampli?er and voltage
supply is normal, the sWitch circuit routes the RF signal
through the ampli?cation path. To set up the ampli?cation
path, the ?rst bypass sWitch 52 is set to pass the incoming
signal to the ?rst diplex ?lter 60. The diplex ?lter separates
the signal into the doWnstream (50-1000 MHZ) signal com
ponent coming from the cable system and the upstream (5-40
MHZ) signal component coming from the customer’s equip
35
ment, Which is directed back to the cable system. A separate
upstream ampli?er 56 and a doWnstream ampli?er 58 are
provided to make up for losses in passive drop ampli?er
DETAILED DESCRIPTION OF THE PREFERRED
EMBODIMENTS
The present invention is a drop ampli?er designed to reli
ably maintain the VoIP signal path during a loss of poWer or a
components and provide unity gain. The doWnstream signal
component originates at the cable supplier, passes through the
normally open contact of the ?rst bypass sWitch 52, the ?rst
40
failure of active amplifying components.
FIG. 1 illustrates a system employing aVoIP drop ampli?er
according to the invention. The cable operator provides com
munication services to a multi-tap point 46. The VoIP drop
ampli?er is connected to the multi-tap connection via a cable
that is connected to the RF signal input connector 44. The
the splitter 64, the signal is routed to the various consumer
equipment, as shoWn in FIG. 1, With the exception of the VoIP
45
the normally open contacts of the second bypass sWitch 54
50
and then to the VoIP output connector 38.
The path for the reverse signal, originating at the consumer
equipment is into the connectors 40a-40g through the splitter
64, into the second diplex ?lter 62, through the loW frequency
ampli?er 58, then through the ?rst diplex ?lter 60 and through
Connected by cables to the output connectors are various
devices for utiliZing broadband cable service. Connected to
output connector 4011 is a cable modem 24 supplying an
Internet connection for a personal computer 48. TWo inte
grated digital televisions 26 are connected to output connec
tors 40b and 400. IDTV sets are television sets With the ability
telephone equipment. The path to the VoIP connector, after
passing through the splitter 64, also passes through the second
bypass sWitch 54. With the second bypass sWitch 54 in the
energiZed condition, the doWnstream signal passes through
VoIP drop ampli?er provides ampli?cation for the forWard
and return signals and splits the signals, delivering them to the
output connectors 38 and 40a-40g.
diplex ?lter 60, the high frequency ampli?er 56, the second
diplex ?lter 62, and into the splitter 64. After subdividing at
55
the normal open contacts of the ?rst bypass sWitch 52. The
VoIP reverse signal ?rst passes though the normally open
contacts of the second bypass sWitch 54 before entering the
to interface With a broadband netWork to receive such services
splitter 64.
as video on demand (VOD) or electronic program guide
(EPG), as Well as broadcast TV. Output connector 40d is
db), With losses in the passive components, such as connec
connected to a set top box 30, Which in turn is connected to a
conventional television set 28. Output connector 40d is con
nected to a set top box 30 that in turn is connected to a
Preferably, the drop ampli?er Will provide unity gain (0
60
return ampli?er 58. Alternatively, additional gain may be
provided by the forWard and return ampli?ers 56 and 58 to
make up for losses external to the VoIP drop ampli?er 20.
conventional (non iDTV capable) television set 28. A set top
box is common for televisions Without iDTV capability. The
set top box interfaces With broadband netWorks to deliver
such services as VOD and EPG to conventional television
sets.
tors, diplex ?lters and splitters, being compensated for by the
ampli?er circuitry comprising the forWard ampli?er 56 and
65
When an abnormal condition, such as a loss of poWer to the
VoIP drop ampli?er or an abnormal operating condition of the
RF ampli?ers 56 and 58, is encountered, the dc current and
US 7,530,091 B2
5
6
voltage sensing circuit 66 switches the bypass sWitches 52
pletely, isolating these components from the signal path. In
this condition, the bypass path 68 is activated, connecting
bypass sWitches 52 and 54 from cycling betWeen the normal
and the bypass condition When the sensed voltage and current
values undergo small ?uctuations.
FIG. 5 is a simpli?ed diagram shoWing an implementation
of the bypass circuitry using relays as the bypass sWitch 52
and 54 components. Each relay is a single pole double throW
only the VoIP output connection to the cable system. If the
overall gain in the normal condition Was unity (0 dB), isolat
ing the components and connecting the input connector 44
normally closed contact When the relay coil is de-energiZed.
When the relay coil is energiZed, the common pole is discon
directly to the VoIP output connector 38 Will restore an essen
nected from the normally closed contact and connected to the
tially lossless communication path through the VoIP drop
normally opened contact. Alternatively, a single double pole
double throW (DPDT) relay can provide the functionality of
the pair of SPDT relays.
and 54 to the normally closed condition, as shoWn in FIG. 3.
In this condition, the path through the diplex ?lters 60 and 62,
the ampli?ers 56 and 58, and the splitter 64 is opened com
(SPDT) type With a common pole that is connected to the
ampli?er 20 for the VoIP consumer telephone equipment
While removing service from the other consumer equipment.
By referring to the simpli?ed schematic diagram of FIG. 4,
the operation of dc current and voltage sensing circuitry can
As shoWn in FIG. 5 the voltage V RELAY, Which is the
output of the voltage sensing circuit 66 as shoWn in FIG. 4, is
applied to the relay coils of tWo SPDT relays 202 and 204.
The common pole of the ?rst relay 202 is connected to the
cable system input connector 44 of the VoIP drop ampli?er
20. When the voltage sensing circuit 66 provides a high level
be understood.
The dc current and voltage sensing circuit 66 monitors the
current provided to the loW and high frequency ampli?ers 56
and 58 (see FIGS. 2 and 3), as Well as the dc poWer supplied
to the VoIP drop ampli?er. The ampli?er voltage is sampled at
20
the VoIP poWer supply connector 42 via a voltage sensing
circuit. The voltage sensing circuit 110 ?lters the dc voltage
and scales the voltage using a voltage divider or other tech
nique knoWn in the art. The voltage at point 118 is then a
scaled value representative of the voltage provided to the unit.
25
This voltage is compared to a reference voltage V REF3 at a
?rst voltage comparator circuit 108. If the scaled voltage falls
beloW the reference voltage, indicating that the supply poWer
is failing or has failed, the voltage comparator 108 generates
a high output signal as its output.
The poWer supplied to the RF ampli?ers (56 and 58 in
When the sensing circuit 66 detects a loss of poWer supply
30
35
ampli?ers 56 and 58 by loWering the voltage supplied to the
ampli?ers at path 116. The resistor 100 is large enough that
the voltage drop across the resistor 100 is easily measurable in
the current sensing circuitry. The voltage drop across the
sampling resistor R1 is ampli?ed at an amplifying stage 102,
Which generates at output 114 a voltage proportional to the
combined current draWn by the RF ampli?ers, and the ampli
?er output 114 is provided to a high current limit comparator
40
45
50
thus maintaining a loss-free connection to the consumer’s
55
VoIP telephone equipment.
In an example implementation, the reverse ampli?er 58
comprises an RF Micro Devices RF2317 integrated circuit
based RF ampli?er, While the forWard ampli?er 56 comprises
an ANADigics Inc. ADA10000 integrated circuit based
at common connection point 120. If any of the three compara
60
output signal, V RELAY, at path 122. The voltage at path 122
is used to control the bypass sWitches 52 and 54 of the VoIP
drop ampli?er 20. The hysteresis of the Schmidt trigger 112
results in the reset point of the Schmidt trigger 112 being
appreciably loWer than the trigger voltage, Which prevents the
be disconnected from the cable signal When the VoIP drop
ampli?er 20 is in the bypass condition.
A complete loss of all poWer supplied to the VoIP drop
ampli?er 20 Will result in disabling the voltage and current
sense circuitry 66. Because the bypass path through the
ampli?er 20 is selected using the normally closed contacts of
the bypass sWitches 52 and 54, the loss of poWer to the VoIP
drop ampli?er 20 Will result in bypassing the de-energiZed
active circuitry and the splitter 64 of the drop ampli?er 20,
output. The high and loW current limits are selected so that
tors generates a high-level voltage output, a Schmidt trigger
circuit 112 trips to removes the voltage supplied at point 122.
OtherWise the Schmidt trigger circuit 112 generates a dc
Because the splitter 64 is bypassed in this condition, the
bypass path 68 is nearly lossless. If the VoIP drop ampli?er 20
is designed for unity gain, the VoIP output connector 38 Will
be supplied With essentially the same signal level in the
comparator 106 generates a high voltage output value, and if
When the current draW anticipated for the RF ampli?ers 56
and 58 is outside normal limits, the respective current com
parator 104 or 106 generates a high output signal.
The outputs from the high limit comparator 106, loW limit
comparator 104, and the voltage comparator 108 are summed
age Will be deactivated as described above, resulting in the
coils of the bypass relays 202 and 204 becoming de-ener
giZed. When the relay coils are de-energiZed, the signal path
through the ampli?ers 56 and 58 and splitter 64, or the ampli
?cation path, is isolated by opening of the normally open
relay contacts. The normally closed contacts of the bypass
bypass condition as in the normal condition. Non-essential
consumer equipment, such as the PC Internet connection, Will
114, is compared to a reference value (V REF1 orV REF2). If
the current exceeds a high current limit value, the high limit
the current drops beloW the loW current limit reference value,
the loW limit comparator 104 generates a high voltage output
signal. When the current is betWeen the high and loW levels,
the high and loW limit comparators generate a loW voltage
voltage or improper ampli?er operation, the V RELAY volt
relays 202 and 204 are then closed to complete a bypass path
68, connecting the cable system to the VoIP output 38.
1 06 and a loW current limit comparator 1 04. In each circuit the
RF ampli?er supply current, represented by voltage output
splitter 64, and to each of the output connectors 40a-40g. The
coil of the second relay 204 is also energiZed, closing its
normally open contact. The second relay 204 completes the
path through the splitter 64 and to the VoIP output connector
38.
FIGS. 2 and 3) passes through a sampling resistor R1, also
designated 100 in FIG. 4. The ohmic value of the sampling
resistor 100 is small, so that the voltage drop across the
resistor 1 00 does not interfere With proper operation of the RF
output voltage forV RELAY, the relay coil of the ?rst relay
202 is energiZed, connecting the input through the ?rst diplex
?lter 60, the high and loW frequency ampli?ers 56 and 58, the
65
broadband RF ampli?er. The comparator circuits 104, 106,
and 108 are implemented using conventional operational
ampli?er circuits, such as the LM2900. The current supplied
to the tWo RF ampli?er circuits passes through a l-ohm
resistor 100, developing a voltage across the resistor 100
proportional to total ampli?er current. This voltage is com
pared to reference voltage supplied to the current comparators
104 and 106 to implement the high and loW current limits
US 7,530,091 B2
8
7
described above. The loW current limit is approximately 180
an input connector for accepting a broadband cable signal
from a cable system and returning broadband signals to
the cable system;
milliamps (mA), While the high current limit is at approxi
mately 300 mA. The nominal expected current draW for the
ampli?er circuitry is 250 mA. The current limit values are
chosen to be consistent With the range of expected currents for
a plurality of output connectors including at least one non
essential output connector and at least one essential
input connectors, the at least one essential output con
the particular ampli?er circuits used in the VoIP drop ampli
?er 20. When ampli?er current is outside of the expected
range of values, the dc current and voltage sensing circuit 66
removes the voltage to the coils of the bypass relays 52 and
54, sWitching the circuit into the bypass condition described
nector including an output adapted for connection to
VoIP telecommunication equipment;
an ampli?cation path connecting the input connector to the
plurality of output connectors, the ampli?cation path
above. After a trip due to an out-of-range current, the VoIP
having:
resets When the current increases to 200 mA or decreases
beloW 280 mA due to the hysteresis of the Schmidt trigger
a diplex ?lter for separating the broadband signal into
return and forWard signals;
112 circuitry. The voltage sensing circuitry conditions the
incoming voltage using ?lters and surge suppressors, and
ampli?er circuitry comprising a forWard ampli?er for
amplifying the forWard signals;
then employs a voltage divider netWork to provide a voltage
a return path for the return signals; and
proportional to the supply voltage. This voltage is compared
a splitter for connecting signals traveling on the ampli
to a reference voltage developed from an integrated circuit
voltage regulator to establish the loW voltage trip point. The
loW voltage limit is approximately 13 volts, With the normal
supply voltage for the VoIP being 15-volts dc. When the
20
?cation path to each of the plurality of output connec
tors;
a bypass path connecting the input connector to the at least
one essential output connector;
supply voltage drops beloW the loW voltage limit, the voltage
a sWitching circuit for sWitching betWeen the ampli?cation
path and the bypass path; and
and current sensing circuit 66 removes the voltage to the coils
of the bypass relays 52 and 54, sWitching the circuit into the
a dc current and voltage sensing circuit connected to the
supply voltage, the VolP resets to use the ampli?cation path
sWitching circuit for to selecting the bypass path upon dc
current and voltage sensing circuit detecting an abnor
When the voltage increases to at least 14 volts due to the
mal condition and for selecting the ampli?cation path
hysteresis of the Schmidt trigger 112 circuitry. The circuit
When the dc current and voltage sensing circuit does not
detect an abnormal condition, the dc current and voltage
bypass condition described above. After a trip due to a loW
components, voltages and currents described above are by
Way of example and do not limit the invention to the particular
components and circuit values detailed.
The dc current and voltage sensing circuit may use other
means of detecting faults in the drop ampli?er circuitry. For
25
30
ampli?er circuitry;
a ?rst comparator circuit for comparing the total dc
current poWering the ampli?er circuitry to a high cur
example, the integrated circuit ampli?ers used to implement
the forWard and reverse ampli?ers may include an output
sensing circuit comprising:
a circuit for detecting total dc current poWering the
35
rent limit and generating a ?rst output based on the
40
a second comparator circuit for comparing the total dc
current poWering the ampli?er to a loW current limit
and generating a second output based on the compari
son, the loW current limit being loWer than the high
current limit;
a circuit for monitoring dc voltage supplied to the
reverse ampli?er and the forWard ampli?er, and
comparison;
signal indicating normal operation of the ampli?er. The dc
current and voltage sensing circuitry could detect the loss of
the normal operation signal and trigger the selection of the
bypass path. In addition to sensing the dc voltage supplied to
the unit, the dc voltage and sensing circuit may sample an ac
supply voltage by rectifying and ?ltering the ac voltage to
obtain a dc voltage representative of the ac supply voltage.
The representative dc voltage may be compared to a reference
and the results of the comparison may be used to control the
bypass circuit.
45
a voltage comparator circuit for comparing dc voltage
supplied to the ampli?er circuitry to a loW voltage
Separate sensing resistors may be provided in the respec
tive current paths supplying the forWard and reverse ampli?
limit and for generating an output based on the voltage
comparison, the abnormal condition being detected
When the ?rst output exceeds the high current limit,
ers. By providing separate sensing resistors, and separate
pairs of loW and high current comparator circuits, the currents
provided to the forWard and reverse ampli?ers can be moni
tored separately rather than as a combined value. The current
set points of set of loW and high current comparators are
chosen based on the expected operating currents for the
the second output is less than the loW current limit, or
voltage supplied to the ampli?er circuitry less than the
loW voltage limit.
2. The VoIP drop ampli?er according to claim 1, Wherein
said ampli?cation path further comprises a reverse ampli?er
respective ampli?er.
In another variation of the VoIP drop ampli?er, the ampli
the output based on the voltage comparison detects dc
50
55
in the path for the return signals for amplifying the reverse
?er circuitry may include a forWard ampli?er but no reverse
signals.
ampli?er. This con?guration is useful When user components
3. The VoIP drop ampli?er according to claim 1, Wherein
the sWitching circuit comprises an input RF sWitch having:
such as a set top box or a cable modem generate reverse
signals at suf?ciently high levels so that ampli?cation of the
return signal from these user components.
It is to be understood that the present invention is not
limited to the embodiments described above, but encom
passes any and all embodiments Within the scope of the fol
a ?rst normally open contact connected to the ampli?cation
60
path; and
a ?rst common contact connected to the input connection,
loWing claims.
I claim:
1. A VolP drop ampli?er for connecting equipment to a
broadband signal, the VoIP drop ampli?er comprising:
path;
a ?rst normally closed contact connected to the bypass
65
the input RF sWitch being operable to sWitch betWeen
connecting the ?rst normally open contact to the ?rst
common contact, and connecting the ?rst normally
closed contact to the ?rst common contact.
US 7,530,091 B2
10
4. The VolP drop ampli?er according to claim 3, wherein
the switching circuit comprises an output RF sWitch having:
a dc current and voltage sensing circuit connected to the
sWitching circuit for selecting the bypass path upon the
dc current and voltage sensing circuit detecting an
a second normally open contact connected to the ampli?
cation path;
abnormal condition, and for selecting the ampli?cation
path When the dc current and voltage sensing circuit
a second normally closed contact connected to the bypass
path; and
detects the absence of an abnormal condition.
6. The VoIP drop ampli?er according to claim 5, Wherein
said dc current and voltage sensing circuit further comprises
a second common contact connected to the at least one
essential output connector, the output RF sWitch being
operable to sWitch betWeen connecting the second nor
a ?rst circuit for sensing a ?rst dc current poWering the
forWard ampli?er;
mally open contact to the second common contact, and
connecting the second normally closed contact to the
a second circuit for sensing a second dc current poWering
the reverse ampli?er;
a ?rst comparator circuit for comparing the ?rst dc current
second common contact.
5. A VolP drop ampli?er for connecting equipment to a
broadband signal, the VoIP drop ampli?er comprising:
poWering the forWard ampli?er to a ?rst high current
limit and generating a ?rst output based on the compari
an input connector adapted for accepting a broadband
cable signal from a cable system and returning broad
band signals to the cable system;
a plurality of output connectors, the output connectors
having at least one non-essential output connector and at
least one essential output connector, the at least one
son;
a second comparator circuit for comparing the ?rst dc
current poWering the forWard ampli?er to a ?rst loW
current limit and generating a second output based on
20
essential output connector including an output adapted
for connection to VoIP telecommunication equipment;
an ampli?cation path connecting the input connector to the
current poWering the reverse ampli?er to a second high
current limit and generating a third output based on the
plurality of output connectors, the ampli?cation path
having:
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current poWering the reverse ampli?er to a second loW
current limit and generating a fourth output based on the
a reverse ampli?er for amplifying the return signals; and
30
one essential output connector;
path and the bypass path; and
comparison, the second loW current limit being loWer
than the second current high current limit;
output generating circuitry for generating an abnormal
condition detection output for detecting an abnormal
condition, the abnormal condition detection output
?cation path to each of the plurality of output connec
tors;
a bypass path connecting the input connector to the at least
a sWitching circuit for sWitching betWeen the ampli?cation
comparison;
a fourth comparator circuit for comparing the second dc
a diplex ?lter for separating the broadband signal into
return and forWard signals;
a forWard ampli?er for amplifying the forWard signals;
a splitter for connecting signals traveling on the ampli
the comparison, the ?rst loW current limit being loWer
than the second current high current limit;
a third comparator circuit for comparing the second dc
35
depending on the ?rst output, the second output, the
third output, and the fourth output.
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