Catv Multi-tap Distribution Box With A Key Actuated Connector For Each Of A Plurality Of Taps

Abstract

A multi-tap distribution box for a community antenna television system. The box is interposed in a primary cable carrying video and radio signals from a master station to subscribers who are linked to the cable by drop lines coupled to the taps. To prevent illegal taps, security keys are provided, each of which is insertable in a keyway associated with a tap. When fully inserted, each key is received by a connector whose circuit, in the absence of a key, is adapted to terminate the related tap and thereby prevent the transfer of signals to the subscriber, the connector circuit, in the presence of a key, rendering the tap operative. A guard system is provided which in one phase blocks all keyways to prevent the entry of keys therein, in another phase unblocks the keyways to permit insertion of keys in selected keyways, and in a third phase captures the inserted keys to prevent removal thereof, and also blocks the remaining keyways to preclude the entry of additional keys. Also provided are means to lock the guard system in the third state to maintain status quo, whereby the only taps which are operative are those which are legal.

Description

BACKGROUND OF THE INVENTION

This invention relates generally to multi-tap distribution boxes for community antenna television systems, and more particularly to a distribution box incorporating security means to prevent illegal taps.

In a community antenna television system (CATV), a primary line in the form of a coaxial cable serves to conduct television and radio signals from a master station for distribution to the homes, offices, and other facilities of subscribers in the community being serviced. Distribution boxes are installed at various points along the cable. These boxes in some instances are placed in outdoor or underground lines, or they may be installed in the basement of an apartment house, in which event they are more readily accessible. Drop lines taken from the taps on the distribution boxes serve to carry the signals to the subscribers' television sets.

The problem to which the present invention is addressed is that arising from illegal taps. When a subscriber fails to pay his bill, or when he moves away or discontinues his subscription, his drop line is removed by a serviceman from its tap on the distribution box. The free tap is then capped with a plug which incorporates a load resistor to match the impedance and balance the line.

One intending to make an illegal tap has merely to remove the plug and connect a drop line to the tap, thereby obtaining CATV signals without payment for the service. Heretofore, in order to detect illegal taps, it was necessary to police the system. But such direct visual inspection involves considerable expense, particularly in large CATV systems having thousands of subscribers dispersed over a large area. While attempts have been made to reduce the considerable loss of revenue resulting from illegal taps by means of identification tags which can only be removed by cutting the wire to which the tag is attached, tag systems involve an inspection and auditing procedure which is expensive to maintain.

Another approach to reducing illegal taps is that disclosed in U.S. Pat. No. 3,573,702, in which those taps not in use are terminated by security plugs which are not easily removable except by a special keyed tool. But once this tool or an improvised device serving an equivalent function falls into the hands of an illegal tapper, the security plug may be readily removed.

With the rapid expansion of CATV facilities now in progress, there is an increasing need for a tamper-proof, multi-tap distribution box which requires no special tools to operate, and which as a practical matter, makes it virtually impossible to effect an illegal tap.

SUMMARY OF THE INVENTION

In view of the foregoing, it is the main object of this invention to provide a multi-tap CATV distribution box to which subscriber drop lines may be coupled, the box including security means to render operative only those taps which are legal.

More specifically, it is an object of this invention to provide a distribution box of the above-described type, in which illegal taps are prevented by security keys, each of which is insertable in a keyway associated with a tap, the key being received in a connector whose circuit renders the tap operative only when a key is present.

A significant feature of the invention is that the security keys not only function to render taps operative, but they also serve as indicators to identify the legally operative taps. Thus in practice, the keys may be numbered or otherwise marked, to facilitate auditing and record-keeping.

Also an object of this invention is to provide a distribution box of the above type which is tamper-proof, locking means being included to prevent the extraction of security keys from operative taps and to preclude the insertion of additional keys.

Still another object of the invention is to provide a distribution box in which the taps are rendered operative by means of contacts, such as those provided by printed circuit board connectors whose circuits are arranged to normally terminate and ground the associated taps, the termination of each tap being lifted when a key is inserted in the connector associated therewith. An important aspect of this arrangement is that the key-actuated connector includes auxiliary contacts whose open or closed state may be used to reflect the status of the tap and to provide an appropriate indication thereof at the master station.

Briefly stated, these and other objects of the invention are accomplished in a CATV distribution box having a plurality of taps and a keyway associated with each tap, each keyway when unblocked, providing a passage leading to key-actuated connectors whose circuit in the absence of a security key is adapted to terminate the related tap and thereby prevent the transfer of signals from the primary CATV cable to a drop line coupled to the tap. When a security key is inserted in the connector, the circuit produced thereby renders the related key operative.

A guard system is provided which in one phase blocks all tap keyways to prevent the entry of keys therein; in another phase unblocks the keyways to permit key insertion in selected keyways; and in a third phase captures the inserted keys to prevent removal thereof and also blocks the remaining keyways to prevent the entry of additional keys. Also provided are means to lock the guard system in the third phase to maintain status quo, whereby the only taps which are operative are those which are legal.

OUTLINE OF THE DRAWING

For a better understanding of the invention, as well as other objects and further features thereof, reference is made to the following detailed description to be read in conjunction with the accompanying drawing, wherein:

FIG. 1 is a perspective view of a CATV multi-tap distribution box in accordance with the invention;

FIG. 2 shows the same box, but with its casing made transparent to reveal the inner guard plate and circuit chassis, as well as the connector array;

FIG. 3 is an exploded view of the distributor box;

FIG. 4 is a schematic circuit of a connector with a key inserted and a connector with a key withdrawn;

FIG. 5 is the schematic circuit of the electronic multi-tap system contained in the chassis of the distribution box, and

FIG. 6 is a perspective view of another embodiment of a CATV multi-tap distribution box according to the invention.

DESCRIPTION OF THE INVENTION

Referring now to the drawings, there is shown a multi-tap distribution box, generally designated by numeral 10, the box being interposed in a primary line or coaxial cable 11 of a CATV system. In practice, the box may be installed on overhead or underground lines or in lines passing through buildings.

Distribution box 10 is provided with four ports or taps 12A, 12B, 12C and 12D, which are connectable to subscribers by means of drop lines provided with suitable tap couplers, such as drop line 13 which is shown in FIG. 1 coupled to tap 12A. While a box with four taps is shown, it is to be understood that in practice the box may have a greater or smaller number of taps, to meet system requirements.

The salient feature of the present invention resides in the fact that no tap on the box is operative unless a security key K is fully inserted in a slot or keyway associated with the tap. Otherwise, even though the tap is unplugged and physically coupled to a drop line, it is electrically disconnected from the drop line, and no signals from the cable are transferred thereto. In a conventional box, if one can obtain access to an available tap, signals are transferred to the drop line the moment it is coupled to the tap, whereas in the present invention, transfer takes place only when a security key is properly inserted.

Each of taps 12A to 12D has a slot or keyway adjacent thereto; namely keyways 14A to 14D. When unblocked, the keyways provide passages for keys K leading to correspondingly positioned taps 15A to 15D. These connectors are mounted on an insulating baseboard 16, supported within a chassis 17. As best seen in FIG. 2, taps 12A to 12D may be mounted on top of chassis 17 and project through openings in the casing 18 of the box. The circuit components associated with the connectors may be mounted on the undersurface of baseboard 16.

Connectors 15A to 15D may be of the printed-circuit (PC) board, edge-mount type, and include two parallel rows of flexible contacts arrayed on opposing sides of the connector. In one row, there are contacts 1, 2 and 3, and in the other row, there are contacts 4, 5 and 6, which in the absence of an inserted key, engage the corresponding contacts in the first row. Thus, contact pairs 1-4, 2-5 and 3-6 constitute normally closed switches.

Each key K, as best seen in FIG. 3, is fabricated of PC insulating-panel material, and is contoured to define a rectangular head K.sub.1, a central shank K.sub.2 and a rectangular foot K.sub.3 extending laterally from one side of the shank and forming with head K.sub.1 an indentation K.sub.4. Secured to the lowermost edge of foot K.sub.3 is a small conductive pad 19 which is so placed that when a key is inserted in the connector, foot K.sub.3 is then interposed between the two rows of contacts to break the connections therebetween, whereas pad 19 bridges contacts 1 and 2 in the first row to electrically interconnect these contacts. The configuration shown in FIG. 3 represents only one of many possible ways of arranging pads or other means of effecting a connection between selected contacts.

We shall now, in conjunction with FIG. 4, consider the circuit associated with the connectors. Connectors 15A and 15B are shown, each having contact pairs 1-4, 2-5, and 3-6. A coil 20 supplies CATV signals derived from the primary line, to the number-1 contacts of both connectors. The number-5 contacts of the connectors are connected directly to ground, whereas the number-4 contacts are connected to ground through an impedance-matching resistor 21. The number-2 contacts of the connectors are connected to the respective subscriber taps (12A and 12B).

In the case of connector 15A, a key K is inserted, hence the signal applied to its contact 1 is fed by bridging pad 19 to contact 2, and from there to the subscriber tap 12A. Hence, with a key inserted in connector 15A, tap 12A is fully operative and serves to transfer CATV signals to a drop line coupled thereto.

When, however, the key is absent, as shown in the case of connector 12B, the subscriber tap 12B is grounded through contact pair 2-5, and signal coil 20 is terminated by impedance-matching resistor 21b through contact pair 1-4. Thus even though tap 12B may be physically coupled to a drop line, no signal is transferred thereto.

The auxiliary contact pair 3-6 is open when key K is inserted (see connector 15A) and closed when key K is withdrawn (see connector 15B), thereby indicating the operative or inoperative status of the tap. These auxiliary contacts may be used with associated circuitry to provide a feedback that may be sensed at the master station to monitor or audit the taps in the system or for other purposes.

Thus the security keys K function to render the taps operative. The heads K.sub.1 of the keys may have numbers or other indicia thereon to facilitate inspection and auditing of the distribution boxes. But the keys by themselves do not prevent illegal taps, for if the keys fall into the hands of illegal tappers, they could be used to provide unauthorized service. It is necessary, therefore, to include means that restrict the insertion and removal of the security keys to authorized service personnel.

This is accomplished by a slidable guard plate 22, which, as shown in FIGS. 2 and 3, is shiftable in the longitudinal direction to the left or right along the underface of casing 18 within limits determined by guide pins 23 and 24 which project through elongated slots in the plate.

Guard plate 22 is provided with marginal notches 25A, 25B, 25C and 25D, which cooperate with keyways 14A to 14D, respectively, such that when the plate is shifted to its leftmost position, as shown in FIG. 2, the notches are out of registration with the keyways and the plate then partially blocks the keyways, whereas when the guard plate is shifted to its rightmost position, the notches are in registration with the keyways, which are then unblocked.

The dimensions of the guard plate relative to the position and width of the keyways is such as to leave a section of the keyways exposed, so that blockage thereof is only partial. The exposed section of the keyways is sufficiently broad to admit shank K.sub.2 of the security key. Hence if a key is inserted in a keyway when the keyways are unblocked, and the guard plate is thereafter shifted to block the keyways, the guard plate will pass through indentation K.sub.4 of the inserted key K, and its movement will not be impeded thereby. But once the guard plate lies within the indentation, the key is captured and cannot be withdrawn.

Guard plate 22 is provided at its right end with a hasp 26 which projects through a slot 27 in housing 18 and cooperates with a fixed housing bracket 28, such that when the guard plate is in its leftmost position (FIG. 2) in which keyways are blocked and the inserted keys are captured, hasp 26 is then aligned with bracket 28. At this point, the two members may be locked together by a padlock 29, as shown in FIG. 1, thereby maintaining the status quo. In this locked condition, one cannot remove or add security keys, and only those taps are operative which have their security keys inserted in their associated keyways. As a consequence, one coupling a dropline to an available tap would receive no signal.

Thus the guard system goes through the following three phases of operation:

PHASE A. In this phase, keys K lie only in those keyways associated with legal subscriber taps, these keys being captured by the guard plate which occupies its closed (left) position. The other keyways are blocked so that no additional keys may be added. This phase remains unchanged until a need arises to alter the subscriber connections to the box.

PHASE B. In this phase, which takes place when a need arises to alter the subscriber connections, the guard plate, having been unlocked, now occupies its open (right) position, permitting keys to be inserted or removed, since the keyways are now unblocked. This is the phase which permits a service man to set up the box so as to supply signals to authorized subscribers and to disconnect the taps from cancelled subscriptions. When this action is completed, we move into Phase C.

PHASE C. In this phase, the guard plate is again returned to its closed position, and the plate is relocked, thereby maintaining the status quo and preventing illegal taps.

In FIG. 5, there is shown the basic circuit for a multi-tap distribution box. The CATV cable 11 is connected to the input terminal 30 which is coupled to output terminal 31 through main coil 32. The CATV signal is distributed to various tap points by means of a circuit-tree composed, inter alia, of signal splitting coils 33, 34, 35, 36 and 37. In the arrangement shown, coil 37 is coupled to connectors 15A and 15B in a circuit similar to that shown in FIG. 4. Obviously, the number of splits involved depends on the number of output taps on the box.

Referring now to FIG. 6, there is shown another preferred embodiment of a distribution box and security-key arrangement in accordance with the invention. The box is provided with two rows of taps with four taps in each row. It will be seen that the taps identified by numbers 1, 3, 5 and 7 in one row, are staggered with respect to taps 2, 4, 6 and 8 in the other row, to allow more room for drop-cable connections.

In the arrangement shown in FIG. 6, the CATV cable is connected to the sides of the box, not to the ends as in FIG. 1. Associated with each tap is a keyway for receiving a security key. In the arrangement shown, keys are inserted in the keyways associated with all taps except taps 6 and 8, the keys therefor being withdrawn. It will also be seen that the keys have identifying numbers thereon. Numbered keys which are not in use may be retained as an office record of disconnects.

In practice, one may hook up a series of distribution boxes to provide a greater number of taps at a particular location in the CATV system. If necessary, amplifiers may be interposed between boxes to maintain the desired signal level.

It is to be understood that circuit configurations other than those shown in FIGS. 4 and 5 may be used for dividing the CATV signal among the available taps. Though the contacts shown in FIGS. 2 and 3 are supported in printed-circuit connectors, in practice, these contacts may be directly riveted or otherwise attached to the insulating baseboard.

FIG. 1 shows a customer drop cable attached to a tap on the distribution box by means of a screw-on cable connector. One bent on tapping illegally, could therefore unscrew a legal connector from the tap and attach his own drop cable to that tap. To eliminate this possibility, the box could be pre-wired with all drops hard-wired at the time of installation.

Thus the present invention, which requires the use of security keys to render a tap operative, makes possible rapid connects and disconnects and it provides office audit controls as well as eliminating illegal taps and reducing installation costs.

While there have been shown and described preferred embodiments of a CATV multi-tap distribution box in accordance with the invention, it will be obvious that many changes and modifications may be made therein without departing from the spirit of the invention. For example, the connectors and keys need not be the PC type, and other suitable forms may be used, as long as the keys are shaped so as to facilitate their entrapment by the guard plate.

Claims

We claim:

1. A multi-cap distribution box adapted for insertion in a primary CATV cable carrying video, radio and other signals, said box comprising:

A. a plurality of taps to which drop lines may be coupled for connection to subscribers,

B. a key-actuated connector associated with each tap, each connector having a circuit which in the absence of a key connects the tap to ground and which in the presence of an inserted key couples the tap to said primary cable to effect a transfer of signals to said drop line,

C. a keyway associated with each tap to provide a passage for said key leading to the related connector, and

D. guard means selectively to block or clear all of the keyways simultaneously.

2. A box as set forth in claim 1, wherein said guard means is constituted by a shiftable guard plate which may be locked in its blocking state.

3. A box as set forth in claim 2, wherein said guard plate in the blocking state entraps inserted keys.

4. A box as set forth in claim 3, wherein said keys each have an indentation engaged by said guard plate.

5. A box as set forth in claim 1, wherein said keys are provided with heads carrying identification data.

6. A box as set forth in claim 5, wherein said connectors are constituted by two rows of contacts which normally engage each other.

7. A box as set forth in claim 6, wherein said keys are fabricated of insulating material which when inserted in the connectors, separate the rows of contacts, said keys having a conductive path therein to interconnect two of the contacts in one row.

8. A box as set forth in claim 7, wherein said keys include an indentation to facilitate entrapment of the guard plate, said indentation being formed between said head and a foot extending laterally from a shank connected to the head.

9. A box as set forth in claim 8, wherein said connectors in the absence of a key connect an impedancematching resistor to terminate the signal source.

10. A box as set forth in claim 9, wherein said connector includes auxiliary contacts which are interconnected only in the absence of a key, to indicate the status of the associated tap or for other purposes.