US2564125A - Selecting system - Google Patents

Description

Patented Aug. 14, 1951 UNITED STATES PATENT OFFICE SELECTING SYSTEM Milton E. Mohr, New Providence, N. J., assignor to Bell Telephone Laboratories, Incorporated, New York, N. Y., a corporation of New York Application July 9, 1948, Serial No. 37,858

4 Claims. 1 1

vThis invention relates to improvements of selecting systems and more specifically to improvements in selecting systems wherein a saturable inductance is used to increase the speed with which a circuit is selected.

One of the primary objects of the invention is to increase the speed with which a circuit is selected for use from a plurality of lines, trunks, or other selectable circuits, while at the same time rendering all the other circuits of said lines, trunks or other selectable circuits unselectable.

Asecond object of the invention is to utilize an inductance as a common impedance to a plurality of space discharge tubes, representing selectable circuits in such a manner that the inductance becomes saturated immediately after a tube ionizes, thus removing the inductive impedance of the saturated inductance and allowing the current in the space discharge tube to increase rapidly.

Another object of the invention is to utilize a saturating inductance so as to increase the speed of operation of the selecting system. A furtherobject is to use asaturating inductance in combination with a plurality of space discharge tubes such that when one tube begins to ionize, the saturating reactance quickly acts to preclude any other tube from ionizing; each space discharge tube being individual to one vof aplurality of selectable circuits.

Another object of the invention is to improve the operation of selecting systems generally.

An additional object is to make use of both the inductance and the resistance of the common inductive impedance to prevent other than one space discharge tube from ionizing.

The invention consists of a selecting system of circuits, each individual circuit having a gas tube and a saturable inductance impedance common to all the gas tubes. A voltage is applied commonly to all the tubes causing one of them to ionize. The mathematical odds are extremely high that only one will ionize. When one tube ionizes, the rising current will produce a drop in voltage across the common impedance and thus lower the voltage across the discharge gaps of the remaining tubes, eiectively preventing them from ionizing. The current flowing through the tube that has ionized can be made to operate relays in the circuit individual to the said ionized gas tube.

There are in theprior art one or more devices whereby a common resistance or a common inductance hasv been used in series with a number of gas tubes connected in parallel withrespect to each other. The function of these devices has been to preclude more than one tube from ionizing.

In the instance of the common resistance, however, there was a chance that more than one tube would ionize. To correct this deficiency a common inductance with resistance was used. The probability of more than one tube ionizing is considerably less than in the case where a resistance alone is used. But the use of the inductance presents a problem, e. g. that the current was prevented, due to inductance in the common impedance, from rising rapidly to a sufficient value to operate relays after the tube had ionized.

The objects of this invention are accomplished by causing the saturable inductance to become saturated immediately after the tube is ionized, thus allowing the current to increase to its full operating value much more quickly. Consequently, in applicants invention there is less time lag between the ionizing of the gas tube and the operation of the relay than can be effected by use of a resistance or an ordinary inductance. The ionization of one tube, the transfer of its discharge, and the operation of the associated magnet such as H0, III, or H2 may therefore be made to occur more quickly. Although the time saved may not, at first glance, seem consequential, it may amount to several tens of milliseconds, a time saving which may be of considerable consequence in the telephone switching art wherein substantial expenditures may be justified in order to save small amounts of time, it being noted in the present instance that the time saving is accomplished at substantially no increased cost, in fact, it may be accomplished at an actual decrease of cost. The saturated inductance will inherently have a resistance of some value. This resistance is so calculated as to provide for a voltage drop across said resistance after the tube has ionized and the elect of the inductance has become unimportant due to the leveling off of the current. Such a voltage drop will lower the applied voltage across the discharge gaps of the other gas tubes to a point suflicient to keep them from ionizing.

The aforementioned features and other features of the invention will be described more fully in the following detailed speciiication.

This invention is applicable generally to selecting and connecting systems but is disclosed in the drawing as used with a cross-bar type of telephone system. For further explanation of a escales 3 cross-bar system, reference is made to patent to Reynolds 2,021,329 of November 19, 1935.

Referring to the drawing the subscribers lines 10 |02, etc., appear in the vertical rows and the outgoing lines appear in the horizontal rows 103, |015, |05, etc. Individual line raleys |09, |01, etc., and switch hold `magnets |08, |09, etc., represent the subscribers lines, and select magnets H0, ||1, ||2, etc., represent the outgoing circuits. Each outgo-ing circuit is also represented by a space discharge tube H3, |14, H5, etc. Although several known gases are suitable, it has been found that argon filled tubes give satisfactory results. Ionization in the tube rst occurs across the two cathodes |22, 1|@ and then transfers to the anode |29. The anodes of all the tubes are electrically connected together through condensers |32, |33, 130, etc., which condensers are all connected to a common point. The left cathodes 122, 123, |20, etc., of the tubes are all electrically connected to negative battery |28 through armature of relay |26. The starting electrodes H6, IIS, ||9, etc., of the tubes are electrically connected through test conductors ||1, |20, 12|, etc., respectively, through armatures of relays |35, |31, 1&2, etc., respectivel to positive batteries 13 5, |33, 139, etc., respectively. Each of the anodes |29, |39, |3|, etc., is connected to one of the select magnets 1|0, |11, |12, etc., respectively. The saturable inductance |21, which is a common impedance to all the tubes, is connected to negative battery |28. Resistances |50 and 15| are of a value of approximately one megohm. Their purpose is to guard against false operation of one or more oi the tubes which could be caused by leakage currents across the contacts of relay |255 when relay 126 is open. The high resistances |59 and |51 provide a path for any such leakage currents to flov,7 to ground Without developing appreciable voltage at the tube terminals. Consequently, both the cathodes |22, |23, |24 and the anodes |29, |39., 13| of tubes H3, 1|l and H5 are held at ground potential through high resistances and |50 respectively, prior to the operation o f relay |26.

The operation of the invention will now be described in detail. A subscriber of line picks up his receiver. This closes the circuit through lines 10| and the winding of relay 100, energizes relay 10G. A circuit is thus completed from ground through the armature of relay |06, the winding of relay 126, to negative battery, and thence to ground, energizing relay |26, and closing the contacts of relay |26. This places positive |09 volts on the anodes of the tubes through the left armature of relay and the select magnets H0, 1|2, etc. 1t also places negative 59 volts on the left cathodes of the tubes through the right-hand armature of relay 126. Thus there isa difference of potential of 150 volts between the anodes |29, |30, |3| and the cathodes |22, |23, |24 of the tube but this is insufficient to ionize the tubes. There is, however, a positive voltage of batteries 136, |38, |39, etc., applied tothe, starting electrodes H0, HS, ||9 of the tubes through conductors ||1, |20, |2I, etc., respectively. This creates a difference of potential across the cathodes and the starting electrodes of the tubes of batteries 136, |38, |39, etc., and battery |29. This difference of potential is sufficient to ionize the gas between the said cathodes and the said starting electrodes. But only one of the tubes will ionize. The tubes have inherently diiferent characteristics and one of them, tube 113 for example, will begin to pass a little more space cur-l rent than the others. As this initial space current is of an increasing nature, a counter-electromagnetic force is induced in saturable coil inductance |21. This counter electromotive force reduces the applied Voltage across the tubes and restrains the tubes, other than tube ||3, from ionizing. As long as the current through tube ||3 is increasing there will be a counterelectromagnetic force induced in saturable reactance |21 which, acting in cooperation with the resistance of said coil, will keep the other tubes from ionizing. Thesaturable core coil 121 is designed so that immediately after the tube ||3 is drawing sufficient current so that the tube can be said to be ionized, said suiiicient current has saturated the saturable core coil and the current in the tube can then rise to its full operating value unimpeded by an inductance in saturable core coil |21. It is to be noted that the saturable core coil |21 becomes saturated before the current in the tube has reached its full operating value. This feature allows a rapid rise of current in the tube after saturation of the saturable core coil 121 and a subsequent rapid operation of relay H9. Before relay Hcan opcrate, however, the ionization within the tube must transfer to anode |29. This transfer is effected between cathode |22 and anode |29 after ionization has been established between cathode |22 and starting electrode |19. After the transfer is made a completed circuit exists .through positive battery |39, line 140, Winding of select magnet |12, anode 129, across the space gap to cathode 122, line |25, through saturable core cc-il 121, to negative battery |28. Select magnet 12 is operated almost immediately since satura-` ble core coil 121 is saturated and the inductance of said coil is ineffective to restrain the increase of current to operating value.

The operation of select magnet prepares the horizontal row of cross-bar contacts, which appear in outgoing circuit |03, for further operation. Thereafter in any suitable manner a circuit is closed over conductor |4| for the operation of Ahold magnet |08. The operation of hold magnet |08 closes the said cross-bar contacts and establishes a circuit from the subscribers tele.- phone to the outgoing circuit |03. At this time, relay |35 which is under the control of the supervisory relay (not shown) operates to place ground potential upon the starting electrode l and provides a holding circuit to ground for hold magnet |98. Since the voltage of battery 128 is insufflcient to sustain an arc across the gap |22-I I3, said arc is extinguished. Relay |35 will remain energized as long as the subscriber upon line |0| continues his call.

Referring again to hold magnet |03 which has just been energized over lead MI, it can be seen from the drawing that such energization of hold magnet |09 opens lines I0| to deenergize relay |05 which in turn causes relay |26 to deenergize. Deenergization of relay 126 opens the circuit from positive battery 139, armature ofrelay |25, line |40, select magnetv |0, anode |29, space gap to cathode |22, line |25, armature of relay |25, saturable core coil |21, to negative battery |28, deenergizing select magnet 10 and extinguishing tube |13. Y

If the subscriber upon line |02 should attempt to place acall, tube 113 would not be affected, Relay |26 would be operated, in this case, from the ground on the armature of line `relay |01 in the manner previously described in connection with the line relay |06. However, relay |35 is operated so long as the subscriber in line is still talking and therefore the potential on electrode ||6 from line ||1 is ground from the front contact of and since the potential of cathode |22 is only negative 50 volts, there is insufcient voltage to ionize the |22||t` gap in tube H3. Since relays |31 and |42 are unoperated the potentials on electrodes ||8 and ||9 of tubes ||4 and I5, respectively, is positive Volts. The full starting gapuvoltages on tubes||4 and ||5 as described heretofore in connection with tube I|3 is therefore 100 volts and one of these, ||5 for example, operates eventually connecting line |02 to outgoing line I 04 in the manner herein described before.

When the subscriber of line |0| hangs up his receiver the supervisory relay (not shown)A operates to deenergize relay |35. Deenergization of relay |35 opens the holding circuit for relay |08 which then becomes deenergized since there is a positive 50 volts on either side of the winding of relay |08 and therefore no current can flow through said winding. In addition the deenergization of relay |35 places a negative battery |36 on start electrode IIS to make tube H3 again ready for another subscriber. The supervisory relay referred to above, its use in a complete system, and its mode of operation are well known to those skilled in the art; by way of one example out of many which might be cited, reference is made to patent to Clark 1,844,147, dated February 9, 1932, wherein the supervisory relay 202 controls a relay 204 which corresponds to and may be provided with contacts to perform the functions of any one of relays |35, |31, |42 of the present application.

In addition to the saturable core coil |21 acting to keep the tubes, other than tube I3, from ionizing, condensers |32, |33, |34, etc., also act to further decrease the voltage applied across anodes and cathodes of tubes other than tube I3. This is accomplished as follows: When tube ||3 starts to ionize, current passes through select magnet ||0, causing a difference of potential across said select magnet. A current will now from the positive side of said select magnet, along line |40, through select magnet III, and will charge condenser |33. This charging current will produce a voltage drop across select magnet and further decrease the voltage applied to anode |30. Similar circuits and charging currents will lower the anode voltage of tube |l5.

What is claimed is:

l. In an arrangement for interconnecting only one circuit of a rst group of circuits to the same circuit of a second group, the combination comprising a plurality of gaseous discharge tubes each including a main space path and a control space path, a power source, an inductor including a winding magnetically coupled to a magnetizable core saturable by current flow through said winding, said control space paths being connected in a low impedance parallel connection with respect to one another and the combination thereof being connected in series with said power source and said saturable inductor when any one of vsaid first group of circuits requests to be connected to one of said second group of circuits thereby applying an ionizing potential to said control space paths through said saturable inductor, a second power source, a plurality of actuating means individually connected to each of said main space paths through said second power source for interconnecting one of said "6 second 'group of circuits associated therewith to one of said rst group of circuits requesting an interconnection when said actuating means is energized by ionization of its associated main space path, said saturable inductor preventing more than one of said control space paths from being ionized at the same time by developing a potential thereacross opposing the potential of said first power source incident to the ionization of one of said control space paths thereby preventing an ionization breakdown potential from being applied to more than one of said parallel connected control space paths, and said saturable inductor thereafter saturating so as to prevent a high value'surge potential from being developed thereacross due to ionization of one of said main space paths thereby diminishing the time interval during which the actuating means associated with said ionized main space path is operated. A

2. In an arrangement employing a plurality of gaseous discharge devices wherein only one of said devices is to be fully ionized within a short time interval to the exclusion of the other of said devices, each of said devices comprising a main space path and a control space path, a plurality of impedance elements individually connected in series with a different main space path in the power supply circuit therefor, said control space paths being connected into a low impedance parallel connection, an inductor including a winding magnetically coupled to a magnetizable core saturable by current ilow through said winding and being connected in series with said parallel connected control space paths in the power supply circuit therefor, and said saturable inductor preventing more than one of said control space paths from being ionized at the same time by developing a potential thereacross opposing the potential applied to said parallel connected control space paths by the power supply circuit therefor incident to the ionization of one of said control space paths thereby preventing an ionization breakdown potential from being applied to more than one of said parallel connected control space paths, and said saturable inductor thereafter saturating so as to prevent a high value surge potential from being developed thereacross due to ionization transfer to one of said main space paths thereby diminishing the time interval during which the impedance element associated with said ionized main space path attains peak potential thereacross.

3. In an arrangement employing a plurality of gaseous discharge devices wherein only one of said devices is to be fully ionized within a short time interval and each of said devices includes an auxiliary space path and a control space path, said auxiliary space path having a lod impedance element individually connected to the power supply circuit therefor, and said control space path being connected in a low impedance parallel connection, the improvement which comprises an inductor saturable by current now therethrough being connected in series with a power supply circuit for said parallel connected control space paths thereby preventing more than one of said control space paths from being ionized at the same time by developing a potential thereacross opposing the potential applied to said parallel connected control space paths by the power supply circuit therefor incident to the ionization of one of said control space paths so as to prevent an ionization breakdown potential from being paths being connected, into a low impedanceV parallel connection, an inductor saturable by current flow therethrough in series with said parallel connected gaseous paths, a power supply source being connected to said inductor-gaseous space path subcornbination so thatA the ionizing potential for said space paths is applied through said saturable inductor whereby a potential opposing the potential of said power supply source is developed acrosssaid` saturable inductor 'incident to the ionization of one of said gaseous space paths thereby preventing more than one of said space paths from ionizing and said saturable inductor thereaftersaturating due to the magnitude of current ow therethrough so. as to attain peak current ow therethrough yin a short time interval after lock-out.

MILTON E. MOHR.

REFERENCES CITED The Vfollowing references are of recordrin the le of this patent:

vUNITED STATES PATENTS Number Name Date 1,943,524 Godsey Jan. 16, 1934 2,320,076 Hall s May 25,1943 2,326,551 Mohr Aug. 10, 1943

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