US1060308A - Intercommunicating telephone system. - Google Patents

Description

L. D. BARROWS. INTERCOMMUNIGATING TELEPHONE SYSTEM.

APPLICATION TILED MAB..22,1912.

1,060,308, Patented Apr. 29, 1913.

Witnesses.

9 5 C In Ventor Leonll Barrows UNITED STATES PATENT 01 1 101 LEON D. BARROWS, OF NEW YORK, N. Y., ASSIGNOR TO AMERICAN TELEPHONE AND TELEGRAPH COMPANY, A CORPORATION OF NEW YORK.

INTERCOMMUNICATING TELEPHONE SYSTEM.

To all whom, it may concern:

Be it known hat I LEON D. Bannows, residing at New York, in the county of New York and State of New York, have invented certain Improvements in Intercommunicating Telephone Systems, of which the following is a specification.

This invention relates to intereommunieating telcihonc systems, and especially to those which are connected through a trunk line to a central station. It looks chiefly to the provision of such a system in which calls coming over a trunk may be readily transferred from one of the intercommunicating substations to another, without danger of eausin a premature disconnect signal at the eentra station.

The accompanying drawing illustrates diagrammatically one of thearrangements by which my invention may be efi'ectuated.

In the present instance but two stations, X and Y, of an intercommunicating system are shown, these being joined by a-trunk line L, L to a central station (not shown). Each of the local stations has the usual tele- )llOIlO set S, talking current for which may supplied from the common battery. over conductors L through suitable retardation coils C; and is further provided with a contact apparatus K consisting of a series. of keys. Of the keys those designated as m and 7 at each station are for connecting the stations with each other, while keyt serves to connect the local station with the trunk line, and key It is for temporarily holding said trunk line, as will appear later. The keys may be locked in a depressed position by a spring actuated plate, which in moving to look any key releases that last depressed. in their locked position keys m and 1/, through opposite contacts 10 and 11 unite the telephone set of the substation at which thcv are placed with pairs of conductors I) and L multipled to similar contacts throughout the various substations. An extra spring 12, when the keys (I: and 7/ are at the limit of their depression below that in which they are locked, joins the bell of the telephone set of the corresponding station through a contact of the switch hook to conductors 18 and 14 14' leading to a local ringing battery B. The key t at contacts 15 and 10, through conductors L, bridges the telephone set of its station across the trunk, while a third contact 17 at the limit of the kcys downward movement connects the Specification of Letters Patent,

Application flied March 22, 1912.

Patented Apr. 29, 1913.

Serial No. 685,441.

winding of a release relay R, common to all the'substatious of the intercommunicating system, to the battery ll by way of conductors 13 and 18. The holding key- It eonnects, through contacts 10 and 20, the telephone set of its substationnand conductors 18 and 21, the winding of a holding relay R to battery ll. At its front contact 22 relay R controls the introduction, in place of a substation set, of a bridge across the trunk for maintaining against operation the usual disconnect signals at the central station. This bridge consists of a. conductor 23, containing the trunk line ringer O of the intcrcomniunicating system, a condenser 1 and a short circuit. 24 about the condenser closed by relay contact 22. At its back contact 25 relay R, whcn'energized, opens a short circuit QG-about a lockin and release relay R thewinding of whici is included in .the trunk conductor L between the extremityof the holding bridge and the central station. {The front contact 27 of relay R closes a gap in av locking circuit 28 of holding relay R, through back contact 10 of the release relay R and a front contact 29 of the holding relay, this locking circuit being independent of the original energizing circuit through holdin kev h. It will be seen that the relays R and R together furnish an electromagnetic apparatus upon the enerization of which the maintenance of the iolding path depends.

hen a call comes into the intercommunicating system over the trunk line, we will assume that it is answered at substation X, and that a subscriber at substation Y is wanted. The subscriber at X pushes down the key t, which looks and at contacts 15 and 16 bridges the telephone set across the trunk, and talks with the calling party. Upon learning that the call is for Y the holding key h is depress freeing the trunk key If and current fin. ..rom battery B through the winding of relay It, conductor 21, contact 10 of key h, the telephone set of substation X (the receiver being off its hook), contact of key It and conductor 13 to battery. Relay R operates, opening contact and the short circuit of relay R which is at once energized by current over the trunk. When the front contacts 22 and 29 of relay R close. condenser P is short cireuited through 'the former by conductor .24, making etiecti ve the holding bridge of the trunk through ringer O; and the contact 20 com 'iletes thev locking circuit 28 for the holding relay, contact 19 of the release relay R bein normally closed and contact 27 of relay T2 having been made as described. The maintenance of the disconnect signal at the central station is now independent of the connection of the substation sets. The subscriber at station X next depresses the key y, releasing the holding key h. In the extreme position of key y the closin of contact 12 rings the bell at substation from battery B through conductor 14', hook switch of station conductors 31 and L, contacts 11 and 12 of kev 3 and conductor 13. The subscriber at responding, locks down his key 3 and upon removing the receiver from its hook is connected for conversation with the subscriber at X through contacts 10 and 11 of the two keys 1 and conductors L. Upon informing substation Y of the call, the subscriber at X may han up his receiver. The subscriber at Y depresses the trunk key i and contacts 15, 16 bridgehis. telephone set across the trunk. The momentary closing of contact 17 operates the release relay R from batter B by way of conductors 13 and 18, and t is drawing up its armature o Jens the locking circuit 28 of the holding relay R. The latter at contact 22 severs the direct current bridge of the trunk, and at contact 25 restores the 'short circuit of the winding of relay R deenergizing it. Said trunk is thus cleared for transmission between-the callin and called subscribers. Since the rela governin the locking circuit of the ho ding relay is in series with the trunk,it is under the control of the central station operator, who,if theintercommunicating subscribers fail to depress the trunk keys-sutticiently to make'cont-act 17, and thus actuate the release relay R, can cut oil the central station battery by withdrawing the trunk In and thus deeinergize relav R, opening die l ocking circuit of the holding relay at contact 27. Relay R may therefore be considered both as a locking and a secondary release relay.

Circumstances may arise which render my arrangement of the relay R with relation to the other elements of the system of great advantage. For example an pose in a connection as enerally outiined above, the trunk key at being locked down as a result of the previous use of the apparatus, that when the subscriber at Y answered he removed the receiver from its hook beiore depressing the local answering key y. This would cause the telephone set to be connected across the trun throu h the contacts of key t, and were the relay in the holdmg bridge of the trunk, would shunt it by a ow resistance path, causing its release. This would unlock the holding relay opening the bridge 23, 24 and leaving the disconnect signal at the central station dependent upon the connection of the substation set. When the subscriber at Y continued the o )eration of answering the subscriber at X y actuating key 3 thus releasing key t, he would shift the telephone set from the trunk to the local circuit and the disconnect signal would be actuated as a result of the complete removal of the holding means, leading the central station operator to withdraw the trunk plug. But with the system arranged in accordance with my invention, although such a procedure shunts the holding bridge,it does not det'energize the lockin and secondary release relay R This 5 unit circuit may be traced from the juncture of the holding bridge circuit with the trunk line L or one extremity of the holding bridge to contact 15 of trunk key 5 b way of one of the conductors L, thence tli rough Ys telephone set to contact 16 of trunk key t, thence along the return conductor L, to the other extremity of the bridge where it joins trunk line L. The current in the trunk is increased by the decrease of resistance due to the connection of the low resistance loop, and this flowing through the relay winding directly in the trunk insures against release. A similar advanta e is gained by removing the release relay t from the trunk, where it is sometimes placed. For assumin the same sequence of acts on the )art 0 the subscriber at Y, the increase oi current due to the connection of the telephone set across the trunk through the contacts of key t, flowing through the windin of relay t nu series with the trunk 'wouiii ener ize it, breaking the locking circuit of the iolding relay at. contact 10, and, as oefore, giving the disconnect signal at the central station. I have so disposed the release relay that it it independent of variations in the trunk current and the holding means will be effective regardless of the manner in which the subscriber responds.

I claim as my invention:

1. The combination with the local stations of an intercommunicatin system and their telephone sets, of a trunii line for connecting the interconnnunicating system with a central station, means at each local station for connecting its telephone set across the trunk, a ath for current which may be substitute for the telephone set to hold the trunk, and electromagnetic apparatus upon the energization of which the maintenance of the holding path depends, said electromagnetic apparatus having an energizing winding in the trunk line in the path of operatin currents between the central statlon ant intercomuiunicating stations.

2. In a telephone system, a central stution, intercommunicating trunk conductors extending between the central station and interconnnunicating stations, a telephone ill) lot]

ll i

set at the interconiiuunicatin Y stations and means for joining its termina s to the trunk conductors, a trunk holding path connected at its extremities to the trunk conductors and'which may be substituted for the telephone set, and electromagnetic apparatus upon the energization of which the maintenance of the holding pat-h depends, said electromagnetic apparatus havin an energizing winding in a trunk eon uctor between the connection of the holding path and the central station.

3. The combination with the local stations of an intercoinmunicating system and their telephone sets, of a trunk line for connecting the intercommunicating system with a central station, means at each local station for connecting its telephone set across the trunk, a at-h for current which may be substituted or the telephone set to hold the trunk, and electromagnetic apparatus having independently energized windings upon the encrgization of which the maintenance of the holdin path depends.

4. The combination with the local stations of an intercommunicating system and their tele hone sets, of a trunk line for connecting 1 ie intercoininunicating system with a central station, means at each local station for connectin its telephone set across the trunk, a )ath or current which may be substituted or the telephone set to hold the trunk, and electromagnetic apparatus having independently ener ized windings upon the energization of w ich the maintenance of the holding path depends, one of the windings being in series with the trunk line.

5. The combination with the local stations of an intercommunicating system and their telephone sets, of a trunk line for connecting the intercommunicating system with a central station, key apparatus at each local station for connecting its telephone set across the trunk, a path for current which may be substituted for thetelephone set to hold the trunk, and relay apparatus havin a plurality of windings upon the energization of each of which the holding path depends, the circuit of one of which windings is overned by the key apparatus, the circuit 0 another of the windings being in series with the trunk line.

6. The combination with the local stations of an intercommunicatin system, of a trunk line connected therewit a holding bridge for the trunk line, means for closing the ridge and electromagnetic means for opening1 the bridge, said electromagnetic means aving an energizing winding in series with the trunk line between the bridge and central station.

7. The combination with the local stations of an intcrcoinniunicaiing system, of a trunk line connected therewith, a holding bridge for the trunk line, a holding relay for closing the bridge, anda relay controlled by the holding relay and serving when enerized to complete a locking circuit for said oldin relay.

8. Tie combination with the local stations of an intercoinniunicating system, of a trunk line connected therewith, a holding bridge for the trunk line, a holding relay for closing the bridge, and a locking relay controlled by the holding relay and serving when energized to complete a locking circuit for said holding relay, the locking relay being energized by current over the trunk line.

9. The combination with the local stations of an intercommunicatin system, of a trunk line connected therewit i, a holding bridge for the trunk line, a holding relay for closing the bridge, and a locking relay controlled by the ho ding relay and serving when energized to connlete a locking circuit for said holdin re ay, the holding rclay being energizer. by local current and {he locking relay by current over the tlllllh inc. 10. The cgpnbination with the local stations of an intercoinniunicating system, of a trunk line connected therewith, a holdin; bridge for the trunk line, in its contacts the holding bridge, relay for the holding relay, and an energizin circuit for the release relay, said circuit being independent of the trunk line.

11. The combination with the stations of an intercommun catin system and their local battery, of a trun l r line connected with said stations, a holding bridge for the trunk line a relay controlling in its contacts the. holding bridge, and a release rela for the holdin relay, said release relay eing ena release ergize from the local battery.

12 The combination with the stations of an intercommunicatin system and their local battery, of a trun r line connected with a relay coiitrolliii; 1

said stations, a holding bridge for the trunk line, a relay controlling in its contacts the holding bridge, and a plurality of release relays for the holding relay, one of said release rela 5 being energized from the local battery an another of said relays being energized over the trunk line.

n testimony whereof, I have signed my name to this specification in the presence 01' two subscribing witnesses, this sixteenth day of March, 1912.

LEON D. BARROWS.

R. S. SU'HJFFE.

copies of this patent may be obtained for ave cent: each, by addressing the "Ooinmintoner of ratenni. Washington, D. 0."

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