A back-up system for the supply of voltage in television cable systems

Abstract: The present invention relates to a back-up system for the supply of electric voltage in television systems to main and secondary amplifiers in case of electric faults by way of switching means, e.g. a relay, triak, a transistor, etc. Said switching means are automatically actuated when an electric fault occurs causing change of direction. The switching means are advantageously located within the trunk and connected to an in/out supply socket or other suitable means. Several systems for the connection of the switching means to the electric source are described

Description: The present invention relates to a back-up system for the supply of electric voltage to main and secondary amplifiers in television cable systems in case of an electricity fault. There is known such a system - the so-called U.P.S system. Said system supplies alternating feeding voltage when no electricity is supplied. The alternating voltage is produced from a number of accumulators and from a cycle converting DC voltage to AC voltage. However the U.P.S. system has many drawbacks. The back-up time is rather restricted. i.e. about 2-3 hours, it has a rather low reliability, it requires an expensive maintenance and high investment costs. US-A-3 909 560 discloses a method and system for providing DC power to booster amplifiers in HF cable networks. It has thus been desirable to design a back-up system, which would overcome the above disadvantages, i.e. should have a rather unlimited back-up time, should be reliable, not require expepsive maintenance and rather low investment costs. It should also be easy in its operation and be suitable to be used in all commercially available cable television systems. The usual television cable system comprises main lines (called "trunk" lines) each one extending from the television station. Each trunk line consists of a cable connecting several main amplifiers (called "trunks") arranged in a so called cascade manner. Each trunk amplifies the signals coming from the station towards the next trunk. Moreover, each trunk transfers said signals to secondary amplifiers lex (line extender), if any, branched out of it. Voltage is supplied to the trunk and to the lex by an electric source being located near the trunk and feeding the trunk. The voltage is suitably supplied via a local power insert (L.P.I.). The electric source is preferably the general electric net form which the voltage is transformed by a transformer to the required voltage. The lex, if any, is supplied with voltage, preferably of 50-68 V, by a voltage bridge via co-axial cables extending from the trunk to the branches of lexes. The above system will be called herein "television cable system". The trunks in this system are located about 500-900 m from each other. The electric source is located about 2 to 35 m from the appropriate trunk. According to the present invention, there is provided a back-up system for the supply of electric voltage to main trunk and secondary line extender amplifiers within a television cable system, in case of electricity supply faults, each main trunk amplifier comprising switching means, characterized in that; the switching means is switchable between two AC voltage sources, a first AC source being a local power supply source and a second AC source being the electricity supply to a neighbouring trunk amplifier, the switching means being actuated when an electricity fault occurs in the local source of electricity to the trunk amplifier thereby switching the source of electricity to the trunk amplifier to the second AC supply. The switching means are automatically actuated in case that there occurs a fault of electricity in one of the electric sources supplying electric current to the trunk. When the electricity fault occurs voltage is switched on the main line between two amplifiers. This is preferably achieved by inserting an additional fuse to the L.P.I. The L.P.I. may then supply feeding voltage to the near trunk and back-up voltage to the previous or following trunk of the cascade. The switching means may be a relay; an element switching current by voltage or outer current (called a "triak" which may be composed of 2 (SCR) units); a transistor; etc. The preferred switching means is an AC relay working preferably on 48-68 V. The advantage of using an AC relay is that the voltage is constant and there is no difference between the "in" and the "out" voltage. However, if required, a DC relay connected to a diode bridge may also be used. The present invention will be illustrated herein especially with reference to the switching means being an AC relay, however as is readily understood it is not restricted thereto. The switching means are advantageously located within the trunk and connected to an in/out supply socket, to a fuse terminal (in case of a MAGNAVOX® trunk) or to a voltage supply selecting socket (in case of a JERROLD® trunk). It is readily understood that the present invention is not restricted to said trunks and that any other commercially available trunk may be used. The kind of connection depends on the switching means and to the kind of trunk amplifier being used. An additional switching means may be located within the trunk or be located thereto by a bridging cable. There are, for example, three suitable systems to connect the switching means to the electric source, namely: 1. Normal "In" back up "Out" system. (System 1) In said system the local power supply is connected to the "In" side of the trunk amplifier and the back-up power is connected to the "Out" side of the trunk amplifier. (This system is not suitable if the fault occurs in the last trunk of the cascade. In this case it is necessary to use a 2-way back-up unit for backing-up the last trunk in the cascade. Such possibility will be described hereinafter). Should there be optical (OPT) receivers in the network it is possible to back-up the receiver and the secondary amplifier by connecting the switching means outside the receiver. In case that the table network consists of OPT receivers only, it is possible to back-up the OPT receivers by external back-up units and to connect the back-up voltage by electric cables. 2. Normal "Out" back-up "In" system. (System 2) In said system the local power supply is connected to the "Out" of the trunk amplifier and the back-up is connected to the "In" side of the trunk amplifier. Thus, there is no need for a 2-way back-up unit for backing-up the last trunk in the cascade, although such a unit may be present. 3. Long distance back-up system. (system 3) Normal "BR" back-up main line. In said system the local power supply is connected to the bridger (one of the 4 exits) and the supply power to the secondary amplifier and trunk amplifier. The back-up power is originating from the main power line. In case of electricity faults in the local power supply, the trunk amplifier will be operated by the back-up voltage received from the main power line. In this case no 2-way back up unit is present or required. Sometimes it is desirable to increase the back-up possibility, in order to avoid over-load in systems 1 or 2, by an additional electricity source. This is suitably being done by connecting said additional electric source to an additional L.P.I. being connected to the first L.P.I. Each L.P.I. has a fuse in opposite directions so that there is no connection between the voltages from both electric sources. The AC relay is suitably built in such a manner that it is actuated by a voltage of 50 V. All the time that the voltage is above 50 V the relay is on "on", i.e. the voltage supplied originates from the original electric source. The moment the voltage is below 50 V the relay is on "off" and electricity is supplied from the back-up electric source and the trunk and the secondary amplifiers are fed by the back-up electric source. The moment the electric fault has been repaired the relay returns to the "on" position and voltage is supplied from the original electric source. The relay may also be connected in the reverse direction and then it works from the last trunk of the cascade towards the first one. In case that system 1 should also enable the back-up of the last trunk of the cascade the system is provided with 2 two-way back-up units, said units being located outside and between the last two trunks of the cascade, each unit being connected via an L.P.I to a separate trunk and to a separate electric source, said units operating in opposite directions one to another, each unit comprising an ignition circuit and a maintenance circuit. The ignition circuit advantageously comprises a diode and a relay. The maintenance circuit advantageously comprises a transformer, diodes and a relay. The relay may be common to both circuits. The L.P.I is advantageously a separate part. However, if desired, the two way back-up unit and the L.P.I. may be built as an integral part. Usually said two-way back-up units are inserted only between the last two trunks of the cascade where they are necessary if the last trunk should be backed-up. However, should anybody be interested therein the two-way back-up units may in addition be inserted between two other or more trunks of the cascade. The two-way back up unit operates as follows: The moment there is an electricity fault in one trunk, the ignition circuit in the two-way back-up unit being connected to the adjoining trunk is ignited and the maintenance circuit of said unit is actuated, after a certain delay, e.g. about 1 sec. and then voltage is supplied to the trunk where the fault occurs. The moment no back-up voltage is required in said trunk the current stops to flow from the back- up unit, the maintenance circuit stops working and the ignition circuit is extincted. The electric source is preferably one which, when no voltage is supplied from the general network to the inlet thereof, is disconnected from the cable system. Otherwise a relay has to be inserted at the inlet or the two-way back-up unit. The above two-way back-up unit can be utilised not only as part of system 1 of the present invention but also for other purposes. Thus it may be utilised for switching voltage when the customer uses above a certain wattage and the drop of said wattage below a certain minimum causes disconnection of electricity. Thus it may be used for an instrument protecting against electrification; for protecting electrical instruments, etc. As indicated above the U.P.S. system commercially being used has many disadvantages. However, nevertheless it may be retained and the system according to the present invention may be used for backing-up said system. The present invention will now be illustrated with reference to the accompanying drawings without being limited by them. Identical parts appearing in the same Fig. are usually referenced once. Identical parts appearing in several drawings are referenced by the same reference numeral. (Figs. 1 - 4 refer to system 1; Figs. 5 refer to system 2; Figs. 6 refer to system 3; and Figs. 7 and 8 refer to all systems.) Fig. 1a shows a block diagram of system 1 according to the present invention; Fig. 1b shows a block diagram of the connection between a trunk and several lexes; Fig. 1c shows a diagram as shown in Fig. 1b provided with two electric sources; Fig. 1d shows a block diagram of the connection between an OPT receiver, 2 trunk amplifiers and several lexes; Figs. 2a and 2b show a relay for the first trunks wherein the relay is in the "on" and "off" position, respectively; Fig. 2c shows a relay for the last trunk wherein the relay is in the "open" position; Fig. 3a shows an electrical circuit of a two-way back up unit; Fig. 3b shows in a schematical manner the connection between 2 adjoining trunks each being provided with a two-way back up unit; Fig. 4a shows the housing of an external back-up unit; Fig. 4b shows the plug connection to the external back-up unit; Fig. 4c shows the switching means in an external back up system; Fig. 5a shows a block diagram of system 2 according to the present invention which operates in the opposite direction to that shown in Fig. 1a; Fig. 5b shows a block diagram of the connection between a trunk and several lexes of the system shown in Fig. 5a; Fig. 5c shows a diagram as shown in Fig. 5b provided with two electric sources; Figs. 5d and 5e show a relay in an one way back-up unit in the "on" and "Off" position, respectively; Fig. 6a shows a block diagram of a system 3 according to the present invention; Fig. 6b shows a block diagram of the connection between a trunk, several lexes and a local power supply of the system shown in Fig. 6a; Fig. 6c shows the power way between normal power supply and back-up power supply in the system shown in Figs. 6b and 6c. Fig. 7a shows an one way back-up unit for Jerrold® trunks; Fig. 7b shows a voltage supply selection socket; Fig. 8a shows an one way back-up unit for Magnavox® trunks; and Fig. 8b shows a fuse socket for a Magnavox® trunk. The system shown in Fig. 1a comprises cable 1 originating in the television station (not shown) connecting trunks A, B, C, D, E and F in a cascade to each other. Each of said trunks comprise a relay 2. On cable 1 are mounted L.P.I. units 3 being connected to electric sources A' to E', respectively. The back-up units between trunks A to E are one-way back-up units. Between trunks E and F are mounted L.P.I. units 4 and 4' being connected via two-way back-up units 5 and 5' to electric sources E" and F', respectively. This constitutes a so-called two-way back up unit. In case that an electricity fault occurs in one of trunks A to E relays 2 are actuated and electricity is supplied from the electric source following said trunk. When the fault occurs in trunk F electricity is supplied from electric source E". The system illustrated in Fig. 1b shows trunk B (by way of example only) comprising relay 2. Trunk B is connected via fuses F1, F2 and F3 by cables C', C" and C"', respectively, to lexes 6 (only one being referenced). Electric source 7 is connected by cable 8 to L.P.I. 9 which is in turn connected to relay 2 located in trunk B. The system illustrated in Fig. 1c is the same as that shown in Fig. 1b with the addition of an additional electric source 7', line 8' and L.P.I. 9'. Electric source 7 supplies voltage to the adjoining trunk and electric source 7' supplies back-up voltage to the preceding trunk in the cascade. The system illustrated in Fig. 1d shows OPT receiver 10 connected to several lexes 6' and connected by cables C' and C" to trunk amplifiers 11 and 12. Electric source 7 supplies normal power to trunk amplifier 11 including lexes 5 connected to a bridger. Electric source 7 supplies also back-up power to OPT receiver 10 and to all lexes 6' connected thereto. L.P.I 9 is connected by 2 fuses providing voltage to trunk amplifier 11 and back-up voltage to OPT receiver 10 and to all lexes 6' connected thereto. L.P.I. 9' is used for forwarding back-up voltage to external back-up unit 14. L.P.I. 9" forwards power to OPT 10 and to all lexes 6' connected thereto. Electric source 8 is connected to external back-up unit 14 at the normal power input side. L.P.I. 9'" Is connected by one fuse to supply voltage to trunk 12 and lexes 6 connected thereto. Optic fiber 15 supplies signals to OPT receiver 10. In order to avoid overload in the course of the back-up time. It is possible to add an additional electric source for backing-up only in the same manner as in Fig. 1c. Figs. 2a and 2b shows an one-way back-up unit for trunks A to E in on and off position, respectively. Fig. 2c shows the on position for an one-way back up unit for amplifier F, i.e. the last trunk in the cascade. The two-way unit illustrated in Fig. 3a comprises : DC relay 16 which may be in two positions. The relay transfers current up to 20 amp. Relay 16 is actuated by a minimum DC voltage of 20 V. It is actuated when there is voltage 0 connected to the earth by a co-axial cable. The outlet of relay 16 is connected to L.P.I. 4' or 4" by cable 17; transformer T1 having a winding relation 1:700 (wire 1:wire 2), wire 1 having an 0.01 ohm resistance. This arrangement is made in order to avoid a voltage drop in the back-up operation. As long as there flows a current through wire 1 of transformer Tl there is present voltage in wire 2 which supplies voltage to relay 16. Transformer T1 receives voltage from electrical source 18; diode D1 which avoids the flow of current between both back-up units in the off position; diode 2 which rectifies AC voltage originating in transformer T1 in the course of the back-up operation in order to supply DC voltage to relay 16; resistor R1 to avoid high voltage drop below the breakdown voltage of Zener diode Zl when relay 16 is in the off position and the far trunk requests a back-up; diode Z1 to avoid high voltage of relay 16; and capacitor C1 which delays the ignition and extinction time of relay 16. Fig. 3b shows trunks E and F each comprising a relay 2. Trunk E is connected on one side via L.P.I 3 to electric source E' and on the other side via L.P.I. 3' and two-way back up unit 5 to electric source E". Trunk F is connected via L.P.I. 4', two-way back up-unit 5 to electrical source F'. When there occurs an electrical fault in trunk F the ignition circuit in unit 5 is ignited and provides voltage for a short time, e.g. 1 sec. When the current is above a pre-determined value, e.g.1 amp. the maintenance circuit in unit 5 is actuated. Thus, voltage is supplied to trunk F. When outside electricity returns to trunk F, relay 2 returns to "on" position and current terminates to flow in unit 5. The maintenance circuit does not operate any more and the ignition circuit is extincted. As indicated above the back-up shown in Figs. 4a - 4c is an external back-up unit 14 used for backing-up OPT receiver 10. Figs. 4a and 4b show housing 20 of external back-up unit 14. There are input sockets 21 and 22. Input socket 21 is for the back-up voltage and input socket 22 is for the voltage supplied by the local power supply. Output socket 23 is connected to a trunk amplifier and OPT via an additional L.P.I. (Not shown). Connectors 21', 22' and 23' indicate the manner in which external back-up unit 14 is connected to the network. Fig. 4c indicates how the switching works between normal power source 24 and back-up power source 25. Fig. 5a shows cable 1 originating in a television station (not shown) connecting trunks A, B, C, D, E and F in cascade to each other. Each of said trunk comprises a relay 2. All L.P.I units 9 are connected to the Out position by 2 fuses directing the supply voltage into 2 directions (See Fig. 5b.) Electric sources A' to F' are connected to the general network via L.P.I. units 9. Fig. 5b shows trunk B (by way of example only comprising relay 2 as back-up unit (normal "Out" and back-up "In"). Lexes 6 are connected as shown in Fig. 1b. Electric source 7 is connected by cable 8 to L.P.I. 9 which is connected to the outside of trunk B. Fig. 5c shows the same system as shown in Fig. 5b comprising in addition electric source 8. Figs. 5d and 5e show an one way back-up unit of the system shown in Figs. 5a - 5c in "on" and "off" positions. (Normal "out" and backup "in"). The system shown in Fig. 6a comprises cable 1 originating in the television station (not shown) connecting Trunks V1 - V6 in cascade to each other. Each of said trunks comprises a back-up unit called normal bridger back-up in/out. Each local power supply PS1 - PS6 is connected to the corresponding trunk into one of the bridger outputs F1 - F4. Power supply 7' is used for back-up only and connected to cable 1 by L.P.I. 9. In order to connect back-up voltage to the two directions of L.P.I. 9 there are present 2 fuses inside said L.P.I. Fig. 6b shows trunk V2 (by way of example only) comprising switching means (relay) 2. Power supply 7 is connected to bridger output F4 (by way of example). Power supply 7 is connected to all lexes 5 being connected to outputs F1, F2 and F3 and to trunk amplifier in truck V2. The back-up power is connected to cable 1. (As in Fig. 6a) When voltage is inserted into a free bridger-output F1 - F4 there is no need to use a L.P.I. 9. Fig. 6c shows the back-up according to the system shown in Figs. 6a and 6b. Power supply 7' is connected to cable 1 between the trunks (as in Fig. 6a). Power supply 7 is connected to bridger output F4 located in the corresponding trunk. Bridger outputs F1, F2, F3... are connected to lexes 6. V1' shows the input voltage socket supplying power to the trunk amplifier only. The back-up unit shown in Figs. 7a and 7b is for a Jerrold® trunk. Relay 2 is inserted into housing 10. Cable 11 is inserted by plug 12 into voltage supply selecting socket 13. The back-up unit shown in Figs. 8a and 8b is for a Magnavox® trunk. Housing A' of relay 2 is connected directly to fuse socket A" of trunk A (not shown). Fuses (F1' - F4') are inserted into housing A', instead of original fuses (F1 - F4). It is possible to use the original bridger fuse sockets (F1 - F4) with different kinds of housing A'.

Claims: A back-up system for the supply of electric voltage to main trunk and secondary line extender amplifiers within a television cable system, in case of electricity supply faults, each main trunk amplifier comprising switching means (2), characterized in that; the switching means is switchable between two AC voltage sources, a first AC source being a local power supply source (C') and a second AC source being the electricity supply (D') to a neighbouring trunk amplifier (D), the switching means being actuated when an electricity fault occurs in the local source of electricity (C') to the trunk amplifier (C) thereby switching the source of electricity to the trunk amplifier (C) to the second AC supply (D') working as a backup supply. A system according to Claim 1, wherein the switching means is an AC relay. A system according to Claim 2, wherein the relay works on 48 to 68 V. A system according to Claim 1, wherein the switching means is a DC relay connected to a diode bridge. A system according to any of Claims 1 to 4, wherein the trunk is a Magnavox® trunk and the switching means are connected to a fuse terminal. A system according to any of Claims 1 to 4, wherein the trunk is a Jerrold® trunk and the switching means are connected to a voltage supply selecting socket. A system according to any of Claims 1 to 6, comprising more than one switching means. A system according to any of Claims 1 to 7, wherein the electric source is connected to the switching means via a local power insert (4,4'). A system according to any of Claims 1 to 7, wherein the electric source is connected directly to one of the non-used bridgers (F4). A system according to any of Claims 1 to 9, wherein more than one electric source is connected to the trunk. A system according to Claim 1, wherein said cable system includes a plurality of trunks in cascade and is provided with 2 two-way back-up units (5,5'), said units being located outside and between two or more trunks of the cascade, each unit being connected via a local power insert to a separate trunk (E,F) and to a separate electric source (E",F'), said units supplying power in opposite directions one to another, with each unit comprising a circuit to initiate switching and a circuit to maintain the back-up supply. A system according to Claim 11, wherein the circuit to initiate switching comprises a diode (D2) and a relay (16) and the circuit to maintain the back-up supply comprises a transformer (T1), diodes (D2,Z1) and a relay (16). A system according to any one of Claims 1 to 11 wherein the backup supply is derived from a preceeding trunk. A system according to any one of Claims 1 to 11 wherein the backup supply is derived from a subsequent trunk. A system according to any one of Claims 1 to 11 wherein the backup supply is derived from a common power transmission line. A unit according to Claim 12, wherein the relay (16) is common to both circuits.

Inventors: ZILBERBERG DAVID, ZILBERBERG, DAVID
Applicants: ZILBERBERG DAVID, ZILBERBERG, DAVID
Application year: 1995
Main classification: H04N7
IPC codes: H04N7, H02J9