US2108909A - Telephone system - Google Patents

Description

Feb. 2 2, 1938.

w. J, VINCENT TELEPHONE SYSTEM Filed May 28, 1936 FlG. 4-

INVENTOR WILLIAM J. VINCENT BY v ATTORNEY Patented Feb. 22, 1938 ZJdSe AUNITED STATES PATENT orginal TELEPHONE SYSTEM William J. Vincent, Rochester, N. Y., assignor to Rochester Telephone Corporation, Rochester, N. Y., a corporation of New York `Appliuitation May 28, 1936, Serial N0. 82,284

2 Claims. (Cl. 179-84) This invention relates to telephone systems yand more particularly to sub-station signalling or ringing arangements for use therein.

In harmonic ringing systems, the number of telephone bells that can be signalled selectively on a party telephone line without a ground connection at each sub-station, is limited to the lnumber of ringing current frequencies available. Four such frequencies are commonly employed in telephone practice but on occasion five such frequencies are used. For urban subscribers the use `of four sub-stations on a-party line affords satisfactory service but in rural districts Where the subscribers are farther apart, more substations are connected to such a line for economic reasons.

In order to obtain selective ringing on p-arty lines having more sub-stations than the available number of ringing frequencies, it is customary to provide pairs of sub-station ringers tuned to the same ringing frequency, the ringers of a .pair being respectively connected between opposite -sides of the telephone line and ground. Such an arrangement is commonly refered to as divided sub-station signalling. In an arrangement of this kind, eight sub-stations on a telephone line can be selectively signalled by the use of four ringing frequencies and ten sub-stations on a line can be selectivelyl signalled when five ringing frequencies are employed. e

In addition to employing the above described harmonic ringing there has been widely used, a ringing arrangement in which alternatingl ringing current is superimposed on direct current,

35 in effect providing a pulsating current. In .such

an arrangement two of the sub-stations of a 4four party telephone line are bridged between one side of the line and ground while the two other sub-stations are similarly connected be- 40 tween the other side of the line and ground. The ringers of these 4sub-stations are properly biased so that a pair thereof respectively connected to the opposite sides of the line and ground, respond to positive pulsating current and the other pair of sub-stations respectively conlnected to the opposite sides of the line respond to negative pulsating current. This arrangement is also referred to as divided ringing.

Both of the arrangements above described af- ;,9 ford satisfactory station signalling when they telephone lines are not exposed to foreign currents from power lines since the inductive disturbance caused by the connection of the ringers to ground will not be objectionableespecially if an. equal number rof sub-stations are vconnected. to each quencies. `While the impedance of 4these. relays 4telephone line is connected to ground in a circuit side of the line. However, anequal number of" bells cannot always be connected. to each side of the line because of the removal of al sub-station on the line due to the subscribers discontinuance of service. If. thetelephone 4line isA thus unbalanced, the noise level. on the line `may` rise to a point Where it will interfere with satisfactory telephone transmission. But evenV if the telephone line is balanced by having an equal number of ringers or .bells connected to its respective sides,.inductive disturbances frompower Wires paralleling the telephone line for even a short distance, will seriously alfect the telephone transmission so that operating companies have resorted to some arrangement for disconnecting the substation bells orfringers, from "ground at al1 times except when ringing current is. applied to the line. Such a result is accomplishecviby pro- Viding a special relay at each sub-station which is actuated by ringing currentto close the circuit of vthe bell to ground only while ringing current is applied to the telephonedine.. These relays are bridged across the'telephone -line and operate in response to all frequencies, Aalthough they operate more dependably lonthe lower freis rather highin order to have as little effect as possible on telephone transmission, there `1s a slight transmission loss resulting therefrom and when automatic ringing.v is used, -thereis anoticeable increase in the tendency for premature tripping of the ringing current., Furthermore, such relays are expensive and' since .their contacts must be adjusted to'have a light Contact pressure,A the cost of maintaining them insuch 3 adjustment is also an appreciable factor.l Fur-- thermore, such a relayhas Vinertia due to its moving parts so that. there isla'nappreciable time lag between the ap'plicationof'.y the ringing irnpulse and the operation of the ringer.

'I'he main feature of the present invention re# lates to the provisionof a ringing arrangement including a gaseous sectionV whichv offers infinite resistance to the passage of current .therethrough until the difference in potential closes .the terminals of the gaseous sectionvrises itoepproximately fifty volts after whichthe .resistance thereof decreases as the voltage across the same increases.

A further feature of the invention relates to the use of an arc discharge device for temporarily connecting the ringer of a sub-station to ground during the time when ringing current is applied to the telephone line.

Other features of the invention will appear from the detailed description and claims when taken with the drawing in which Fig. 1 is a diagrammatic showing of a portion of a telephone system of which only a calling telephone line, a called multiparty telephone line and a link circuit for interconnecting these lines are illustrated; Fig. 2 is a longitudinal section through, and Fig. 3 is an end view of a rare gas device or discharge tube suitable for use at a substation of the system of the present invention, and Fig. 4 is a chart showing the operating characteristics of this device.

At the left hand portion of Fig. 1 there is illustrated a single party telephone line L having connected thereto a substation A of the usual booster type. This line is connectible to a link circuit LK by any suitable manual or mechanical switching means the specific switching means being omitted, as indicated by the broken line connection. It will be understood that this link circuit can be a conventional cord circuit or it can be a connecting circuit of a call distributing system. A satisfactory type of cord circuit for use in the system, is illustrated in. the patent to Slough 1,519,271 granted December 16, 1924 wherein harmonic ringing is provided, but a link circuit such as disclosed in the patent to Martin 1,541,368 granted June 9, r1925 may also be employed where biased ringers at the substation in a party line are to be actuated by pulsating ringing current. l

A called telephone line L2 having four substations or parties thereon is illustrated of which only the substation B having a ringer RI is illustrated in detail. It will be noted that the ringer RI as well as the ringers R2, R3 and R4 of the remaining substations on the line are each connected from one side of the line to ground through an arc discharge device or a rare gas tube IIl to be described. Similarly, the ringers R5, R6, R1 and R8 are likewise connected between the other side of line and ground through an arc discharge device or gaseous tube I0. The ringers RI and R5 may be tuned to respond to ringing current of 16% cycles frequency, ringers R2 and R6 are responsive to ringing current of 331A; cycles, ringers R3 and R1 are responsive to ringing current of 50 cycles and ringers R4 and R8 are responsive to ringing current of 66% cycles. It should be understood however, that these ringers may be of the biased type to respond to pulsating ringing current as is more fully disclosed in the mentioned patent to Martin.

The arc discharge device or rare gas tube I0 for use at certain of the substations, may be of the general construction illustrated in Figs. 2l

and 3, Fig. 2 being a longitudinal section through the tube and Fig. 3 an end View thereof. The device comprises a sealed tube preferably of glass having electrodes II and I2 sealed into the respective ends of the tube and projecting into the interior thereof in the relation shown in Fig. 2. Certain connection terminals I3 and I 4 are attached respectively to the electrodes II and I2. The tube, before it is sealed, is preferably iilled with a rare gas medium such as neon, argon or a mixture of these gases. The construction of the tube and the composition of the gaseous medium therein are more fully disclosed in an application of F. R. Balcar, about to be led by the Air Reduction Co. This tube is so designed that it has a characteristic curve C as illustrated in Fig. 4, that is, the tube offers substantially infinite resistance to the passage of current therethrough until the difference in potential across its terminals I3 and I4 rises to around fty volts, at which time the gas in the gap between the electrodes breaks down and current starts to flow therebetween. As this voltage increases the resistance of the gas decreases with the result that more current flows through the tube. Since the normal voltages existing across the telephone line during conversation is always less than ftyv volts, the ringers have no effect on the telephone transmission over the line.

In the establishing of a telephone call from the substation A on the telephone line L, to the substation B on the called telephone line L2, the subscriber removes his receiver I6 from its switch hook I'I to initiate the call. If the system is a manual telephone system, the initiation of the call, signals a telephone operator who connects one end of the link LK to the line.l If the system is a call distributing system, an automatic switch connects the link LK tothe terminals of the line. The method of connecting the line L to the link has not been illustrated since it forms no part of the invention and is /well known in the art. After the connection of the link LK tothe line L, the operator depresses the listening key I8 to connect her telephone set (not shown). to the line. On receiving the number and party designation of the called subscribers substation, the operator inserts the plug I9 into the jack 20 of the called line 22. The insertion of the plug I9 into the jack 2|] completes a circuit for energizing the cutoff relay 2I of the called line, the circuit being completed through the sleeve contacts of the jack 2l) and plug I9 and through the sleeve relay 2| of the link circuit to ground. The cutoff relay is thus energized and its armatures and'back contacts disconnect the line relay 23 from its line. After this connection of the link to the called line L2, the operator closes ringing key contacts 24 and 25 in the ringing circuit to connectringing current of the proper frequency to signal the called subscrlbers substation B.

The closure of the upper contacts 25, on the actuation of the ringing key, shunts the ringers R5, R6, R1 and R8 to ground over the lower side of the line, tip contacts of the jack 20 and plug I9, conductor 26, upper contacts 25, conductor 21 to the ground connection. However, ringing current of 16% cycles frequency is applied from this frequency source, over conductor 28, contacts 24 now closed, through the normally closed contacts 29, 30 and 3| of the other ringing frequency selection keys, the lower contacts 25, ring contacts of the plug I9 and the jack 20 over the upper side of the line and through all of the ringers RI, R2, R3 and R4 to ground through their respective discharge tubes I0. This ringing current which is at least eighty volts or over, is effective to break down or ionize the gas in the gap between the electrodes I I and I2 of the tubes associated with the last-.mentioned ringers so that the ringing current temporarily passes through all of these ringers but only the ringer RI which is tuned to 16% cycles frequency is actuated. In the event that automatic ringing is employed the removal of vthe called subscribers receiver 32 from its switch-hook is eiective to trip the ringing by a well-known arrangement now shown.

In the present system two connection jacks 2B and 33 are connected to the called line L2. It will be noted that the connections between the tip and ring contacts of thesev jacks and this line are reversed, that is while the upper and lower sides of the line are respectively connected to the tip and ring contacts of the jack 33, the lower and the upper sides of this line are respectively connected to the tip and ring contacts of the jack 20. In this arrangement the jack 2i? may have one numerical designation such as No. 2345 and the jack 23 may have the numerical designation 2346 so that substations having ringers responsive to the same frequency have a different number. In this way the operators routine will be the same whether she is establishing a connection to a four party line or to an eight party line and obviates the need of a reversing key in the link circuit.

When any of the substations Whose ringers R5, RB, Rl and R8 are connected to the ring or lower side of the line are to be signalled, the plug I9 is inserted into the jack 33 and the desired substation ringer is actuated in the manner described above.

From the foregoing it will be seen that the rare gas tube or arc discharge device i9 affords a simple inexpensive means without moving parts, for temporarily connecting the ringer of a called substation to ground during the interval that ringing is applied tothe called line. While selective ringing has been disclosed, it will be obvious that code ringing may also be employed in connection with the present invention.

What I claim is:

i. In a telephone system, a telephone line having a plurality of substations connected thereto, a ringer at each substation, each of certain of said ringers being connected between one side of the line and ground through a gaseous tube and through a condenser in series therewith, each of the remainder of said ringers being connected between the other side of the line and ground through a gaseous tube and through a condenser in series therewith, a link circuit connectible to said telephone line, a plurality of sources of ringing current of different characteristics equal in number to the maximum number of ringers connected to one side of said line, and means including said link circuit for connecting a selected source of ringing current to either of said sides of the line.

2. In a telephone system, a telephone line having a plurality of substations connected thereto, a ringer at each substation, each of Certain of said ringers being connected between one side of the line and ground through a gaseous tube, each of the remainder of said ringers being connected between the other side of the line and ground through a gaseous tube, each of the ringers connected to one side of the line being tuned to respond to a diierent ringing current frequency, a link circuit connectible to said telephone line, a plurality of sources of ringing current of different frequencies, the number of such current sources being equal to the number of ringers connected to one side of said line, and means including said link circuit for connecting a selected source of ringing current to either of said sides of the line.

WILLIAM J. VINCENT.V

Images