US2249154A - Telephone ringing system - Google Patents

Description

July 15,1941; K. L. M AURER 1 2,2

TELEPHDR: RINGING SYSTBI Filed 08c. 8,1939

misc-a einlssn rm rm INVENTOR KL. AMURERv ATTORNEY Patented July 15, 1941 UNITED STATES-- PATENT OFFICE TELEPHONE RINGING SYSTEM Keith L. Mau -er, Rockville Centre, N. Y., assignor to Bell Telephone Laboratories, Incorporated, New York, N; Y., a corporation of New York ApplicationDecember 8, 1939, Serial No. 308,216

4 Claims. (Cl. 179-86) mal conditions, i. e., when the earth potential at the stations, or the inducedpotentlal from adjacent power lines, etc., is not sumciently high, when added to the potential of the central ofiice battery during the idle or talking condition of the line, to break down some or all of the control gaps of the station tubes which in practice requires about 70 volts. If such a breakdown occurs while conversation is in progress, such discharge will cause noise in the receivers of the parties talking. Further, if the interfering voltage occurs in the absence of ringing potential,

it need only rise to a somewhat higher peak value to cause false operation of one or more of the bells connected to the-line.

An object of the present invention is to provide an arrangement employing gas-filled tubes that will function in a satisfactory manner and obviate noise interference and false ringing under abnormally high ground and induced voltage conditions.

A feature of the present invention resides in employing three-electrode gas tubes in which the so-called main gap, i. e., the gap between the anode andeither of the other two electrodes, is non-rectifying, i. e., will permit a current to flow in'either direction with equal facility, in connecting the control electrode and cathode to the two sides of the line in series with a current limiting high resistance, and in connecting the anode to ground through a polarized and biased telephone ringer of a well-known type, the re sistance at each station being connected between the tube and the side of the line which is opposite the side over which current must be transmitted to operate the respective ringer.

The invention will be understood from the following description and appended drawing which show a tube (Fig. 1) having the bilateral main gap characteristics previously mentioned and the method of connecting the tube with the line and ringer to avoid noise interference and false ringing (Fig. 2).

Referring to Fig. 1, the tube l is ofthe usual of a biasing gas-filled type containing three electrodes, two of which, 2 and 3, are semicircular in shape and arranged in a'plane transverseof the major axis of the tube with thestraight edges of the electrodes close, together (of the order of 1 millimeter). The circular edges are preferably turned downwardin a small arc to'preventexcessive blackening of the envelope or bulb adjacent to the electrode.

The upper or outer surface of the two electrodes, .2 and 3, are coated with alkaline earth compounds such as oxides of barium and strontium, and thereafter activated in the usual manner.

These two electrodes constitute the so-called control gap of thetube and in practice break down at or about volts applied thereto.

The third electrode or anode 4 of the tube employed in the present invention, however, differs from the small untreated wire tip used in tubes now in commercial service and which gives these tubes a highly rectifying characteristic, in thatthe present anodeissimilar in shape, size and surface treatment to the other two electrodes, 2 and 3, whereby the gap formed between either electrode 2 or 3 and the anode 4 is capable of passing current in either direction with equal facility.

Inthe present commercial rectifying tubes the nominal main gap breakdown voltage, i. e.,

between the tip of the wire anode and either of the other electrodes in the absence of ionization, is of the order of 1'75 to 200 volts and the voltage necessary to sustain a discharge there between is of the order of '75 volts. These values could be the same and by proper design probably exceeded in the non-rectifying tubes .of the present invention.

Now, referring to Fig. 2, C is a conventional cord'circuit having four selective ringing keys, J. M, W and R which are adapted when individually operated to connect ground to either side of a connected line L and alternating ringing current in series with a so-called biasing battery to the other 'side ofthe line. For example, key

J is adapted to ground the so-called ring con duetor of the it e and connect the negative pole generator to the tip side of the line and key R is adapted to ground the tip of the line and connect the positive pole of the biasing battery in series with the. ringing generator to the ring side.

Connected across the line at the subscribers stations J, M, W and R, in series with current attery in series with a ringing and R break down in the limiting resistances 5, are gas-filled tubes l of the type hereinbefore described having a main ap of bilateral conducting characteristics.

At stations J and M, i. e., the so-called tip parties, one of the control gap electrodes 2 is connected directly to the tip conductor of the line and its opposing electrode 3 is connected to thering conductor in series with the current limiting resistance 5 and at stations W and R,

-i. e., the so-called ring parties, the location of the current limiting resistance is reversed. it being connected between the tip of the line and electrode 2, while electrode 3 is connected directly to the ring.

Completing the circuit arrangement, polarized and biased telephone ringers 6, of conventional type, are connected between ground and the third electrode or anode 4 of the tube I.

ionizationoccurs, which even in present tubes is of the order of 175 to 200 volts. 2

What is claimed is:

1. In a selective signaling system, a line, a plurality of telephone stations, a source of pulsating signaling current, means for selectively connecting either pole of said source to either side of the line and ground and the other pole of said source to the opposite side of the line, biased telephone The operation of the circuit arrangement above described is as follows: If for example it is desired to ring the party R, i. e., the station which responds to positive pulsatingcurrent on the ring side of the line, the operator will close key R, thereby grounding the tip conductor of the line and connecting the positive pole of the biasing battery, in series with the ringing generator, to the "ring side of the line.

- It is assumed that the voltage of the combined battery and ringing generator, during a portion of each cycle, is sufliciently high (70 volts) to fire the control gap of the .tube at eachstation whereby ionization takes place. When this occurs the main gaps of the tubes at stations W to anode 4, assuming, of course, that the voltage is sufiiciently high (75 volts), and current immediately flows to ground at each of these stations through the windings of the respective ringers. The ringer at station R is biased in the usual, well-known manner to respond to pulsating current in this direction but the ringer at station W is biased in the opposite direction and therefore does not respond.

Similarly, the ringer at station W will respond to connection of negative pulsating current to the ring conductor ofthe lineby the operation of key W, but the ringer at station R, being positively biased, does not respond.

Due to the inclusion of the high value current limiting resistance 5 between the ring side of the line and electrode 3 at stations J and M, insufll-' cient main gap current is permitted to flow to actuate the ringers at these stations. If, however, key M is operated, the ring. side of the line is grounded and positive pulsating current is connected to the tip whereupon the control gaps of. all tubes break down as before, causing ionization and current to flow across the main gaps at stations J and M. The ringer at station M is biased to respond to positive pulsating current and therefore the bell at this station will ring but the ringer at station J is biased in the direction of electrode 3' opposite direction and therefore its bell will be silent. For'the same reason as before mentioned, the main gaps of the tubes at stations W and R will not receive sufilcient current, due to resistance 5, to operate the ringers at these stations.

From the standpoint of noise and false operation of the ringers during non-ringing intervals, due to, induced or ground potentials, as previously discussed, the present arrangement is an improvement over the previous arrangement for the reason that the interfering voltage must reach the breakdown potential of the main gap before '75 ringers at each station adapted to respond to and a three-element gas-filled discharge device comprising an anode and two other closely spaced electrodes associated with each ringer and so connected that said closely spaced electrodes are connected to opposite sides of the line in series with the respective high resistances, and said anodes are connected to ground in series with the respective ringers, said discharge devices being so constructed that a bilateral discharge path of substantially equal conducting characteristic exists between said anode and either of said other electrodes, and said resistances are connected in such a manner that at stations whose ringers are desired to respond to pulsating current applied to one side of the line, the respective resistances are connected between the tubes and the other side of the line. I

2. In a four-party selective ringing telephone system, in combination, a plurality of subscribers stations, a biased ringer, a high resistance element, and a gas-filled discharge device compris ing an anode and two other closely spaced electrodes at each station, a source of pulsating ringing current for actuating said ringers, means ior selectively connecting either pole of said source to either side of the line and ground and the other pole to the opposite side of the line, said discharge devices being so constructed that a discharge between the anode and either of' said other electrodes encounters substantially the same impedance to the passage of current in either direction, a connection between each anode and ground including the respective ringer, and connections at each station between the respective opposing electrodes and opposite sides of the line, the connection to the tip of the line at two stations including the respective high resistance elements and at another two stations, said resistance elements being included in the connections to the ring side of the line.

3. In a four-party selective ringing telephone system employing positive and negative pulsating currents, and a three-electrode gas tube, a high resistance and a biased ringer at each station, characterized in this that the impedance of the discharge path between the anode and either of the other two electrodes of said tubes is substantially the same to current flowing therethrough in either direction, in connecting the anode of line, four biased telephone ringers and a threeelectrode gas tube associated with each ringer,

essence 3 anode end either of said electrodes, two of said ringers being connected between their respective anodes and ground in such e manner es to respond to pulsating ringing current in one direction and the other two ringers co'nnected'in a similar manner to respond to current in the opposite direction, a. connection between the cold 10 connected to the other sie electrodes of each tube and opposite sides of the line, means for selectively grounding either side i of the line and connecting pulsating ringing curent of either polarity to the other side, and a high resistance associated with each tube and connected between one of its respective cold electrodes end the side of the line which will be grounded when ringing current of the proper direction to operate the corresponding ringer is URER.

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