Electronic solid state switching device

TITLE

PRIORITY ^?6 6IU. 1385

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<td> 58</td><td>ROME</td><td></td><td> 21326</td><td> 07</td><td> 1 1</td><td> 77</td><td> 1(</td><td>4C</td><td>C</td><td>c</td><td>c</td>

LIMITED COMMUNICATION SPATENTE IN LONDON

IMPROVEMENTS RELATING TO COMMU TATORS I

GREAT BRITAIN DOM.BREV.N. 46865/76 OF 10TH NOVEMBER 1976

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IWIWISTIÌIIU DELL'IMDESTHIfl, OF TRADE B DBLLWIOMTO

PROVINCIAL OFFICE INDUSTRY COMMERCE AND CRAFTS - ROME

MINUTES OF DEPOSIT FOR INDUSTRIAL INVENTION PATENT

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..................... presented to me signed:

1. · Application, stamped by L. 1500 of PATENT FOR INDUSTRIAL INVENTION having for

TITLE

PERFEZIOHAMEOTI RELATED TO THE SWITCHES * ',

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3. · Description In duplo of n ............. $ ......... writing pages.

3. &gt; Drawings, plates n .......... i ........... In duplo.

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B.. Priority document and Italian translation. (with DldArVA)

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9. - Stamp duty from L. 1500

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MINISTRY INDUSTRY COMMERCE AND ARTICULATED______________

Central Patent Office - ROME

Patent application for industrial invention c&gt; C '

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The firm

COMMUNICATIONS 'PATENTS LIMITED .1, * I,

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li English nationality, based in London (Erigland) ari top. House, Lower Regent Street, - electively domiciled at its office T |) c. RACHELI δ Avv.C. EIAMMENGHI - ROME Via Quattro MonΛ

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tane, 31 - applies for obtaining a patent i

for industrial invention having the following title:

SWITCHES REFERENCES.

.a applicant declares that he wishes to reserve rights in Italy deriving from the priority of the ί application

patent filed in England on 10 November

76 to No. 46865/76 pursuant to the International Opal Convention.

To this end, the following is attached:

I) Description in duplo

Letter of assignment ì

3) A drawing board in duplo

4) Att. of vers. of L. 42.000 = of 4.1F&gt;) A revenue stamp of L. 1.500 =

6) A priority document and translation (with £ reservation)

Rome 8 November 1977

Ingi A. (lACtfÌiTAwl! TffkMMENGHl

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517 | ίΑ / 77

Description of the invention having by title:; IFM / ep / 2Op

SWITCHES REFERENCES on behalf of the Company:

COMMUNICATIONS PATENTS LIMITED 'ta: London (England) __:

The present invention relates to switches, and in particular to switches for use in cable broadcast systems, in which subscribers are provided with control devices for selecting any of a plurality of programs.

the

In many cable broadcast systems, switching between programs is achieved by using reed switches. The costs of these reed switches and their control devices are increasing more and more, while the costs of solid state devices are generally decreasing. This made the development of solid state switches desirable.

A switch has already been described comprising a pair of diodes connected in series with opposite polarity, and a solid state device for applying potentials to the connection point between the two diodes, in order to make these diodes yours. * in turn conductive or non-conductive.

This switch already described performs an operation k;

adequate, but the insulation provided by the switch in its open condition (non-passing signals) is ultimately unsatisfactory. the

I 'i

It forms an object of this Invention to make a switch that obvious or mitigates the previous problem.

According to the present invention, a switch is provided which comprises a diode directly connected to the base of a transistor, so that the diode, the transistor and the connection line between them form part of a signal circuit between the terminals. Input and output switches of the switch, and a solid state device for the selective control of the potential of the connection point between the wire and the transistor, in order to make both the diode and the transistor both conductive or non-conductive.

The transistor is preferably part of a series of monolithic transistors, each of which constitutes a component of a respective switching element.

A practical embodiment of the present invention will now be described, by way of example, with reference to the attached drawings, in which:

Fig. 1 represents a schematic diagram illustrating the operation of a switch according to the present invention; is ! L·

Fig. 2 represents a circuit diagram of a switch according to the present invention suitable for functions. i appears in the same manner as that of the switch Ϊ of Fig. 1.

; the

Referring to Fig. 1, the com switch! ì takes an OR gate 1 and an AND gate 2, this gate; ÀND 2 being able to control the passage i That is the stopping of an HF television signal applied to input 3.

The OR gate 1 has two inputs 4 and 5. If none of the inputs 4 and 5 receives an input signal, the AND gate does not allow the signal to pass

HF AND gate 2 receives a further command input 6 from a program selection device controlled by the subscriber. The input 6 can be, as an example, an output of a register of

Displacement controllable by the selection pulses generated by a subscriber, each output of the displacement register being connected to a respective AND gate 2. If input 6 does not receive an input signal, gate 2 does not allow the passage of the HF signal.

In this way, the switch can be controlled by the subscriber through Input 6 and by the system operator through inputs 4 and 5. Normally, input 4 carries a signal, but if you wish to disable the program on the if it inputs 3 to some subscribers, the signal on input 4 would be interrupted and a signal would be fed to input 5 only for those subscribers to whom you want / receive the program.

Referring now to Fig. 2, the Equivalent inputs 3, 4, 5 and 6 of Fig. 1 have been represented with the same reference numbers.

A television signal HF applied to the conductor of the line signal 3 is passed to the user 7

Through the diode 8 and the transistor 9 connected in series only as long as the potential at the point is such as to directly polarize the diode 8 and initialize the transistor 9. A positive potential is normally applied to the line conductor i

The interdiction 4 connected to point 10 through a diode 11 and a resistor 12. A transistor 13 controlled by the input 6 is also connected to point 10.

THE

In the rest condition of the switch, the transistor 13 has zero or negative potential applied to its base, so as to make it negative, so that the potential at point 10 falls to ground, in «

thus terminating the transistor 9 and consequently isolating the output 7 from the output 3. When a positive potential leveled by the capacitor 14 is applied to the base of the transistor 13, the latter is cut off, thus allowing the growth of the potential in point 10 up to the positive level of the line conductor 4. The diode 8 is then polarized directly and the transistor 9 is made to conduct. In this way, the switch is in the working condition and the signals present at the input 3 are passed through to reach the output 7.

The output impedance of the transistor 13 is in derivation between the point 10 and ground. This arrangement improves the attenuation when the transistor 13 leads, i.e. when the switch is at rest.

If it is desired that all subscribers should not be allowed to receive the programs applied to input 3, the positive potential to line conductor 4 is suppressed. Whatever the condition of input 6, diode 8 will not be polarized directly and l input 3 will be isolated from output 7.

If it is desired to allow selected subscribers to receive an otherwise forbidden program, the positive potential is again suppressed to the line conductor 4. Furthermore, the switch of each subscriber to receive the program is however enabled by closing the switch 15;

which is connected to an auxiliary positive power supply 16. The switches of the enabled subscribers then operate normally, as if the line conductor 4 'carried the positive potential. The diode 11 prevents the positive potential of the power supply 16; reaches the line conductor 4. =

Transistor 9 forms an element of a group of six transistors 17; the other transistors of the group ^ form equivalent component parts 9 for the components.

!

imitators who control the other programs.

In the switch described above, a diode takes the place of transistor 9, this from origj.

nor to a T-attenuator having an insulation lower than the two-section L-shaped network described here.

The switch 15 can be a manual switch provided in a distribution center of the pro grams, normally called the switchboard of the prograin mi. Alternatively, by way of example, switch 15 could be remote controlled from the homes of the respective subscribers. This could be useful when a particular program is banned until the subscriber declares that he accepts the fee for that program,