US804862A - Telephone-exchange system. - Google Patents

Description

PATENTED NOV. 21, 1905.

M. G. KELLOGG. TELEPHONE EXCHANGE SYSTEM.

APPLICATION FILED DEG. 20, 1894 wmmkoz: .Jm 4.1622 4 bn ivioamne subscribers lines.

UNITED STATES PATENT OFFICE.

MILO e. KELLOGGQOF CHICAGO, ILLINOIS.

TELEPHONE-EXCHANGE SYSTEM.

Specification of Letters Patent.

Patented Nov. 21, 1905.

Application filed December 20, 1894. Serial No. 532,483.

In the accompanying drawings, Figure 1v shows a divided exchange system and illustrates two divisions of boards with two boards in each division and the circuit connections and apparatus at the central oflice for two switching apparatus of the central-office operator; Fig. 3, the central-oflice-operators test devices, and Fig. 4 the organization at the subscribers station.

Fig. lshows two divisions of boards (A and B) of two boards in each division (A A and B B for two divisions of lines A and B. Each line has a switch on each board of its division of boards and on one board of the other division of boards, according to my divided exchange system. The switches are represented at s s, &c. Each switch has two contact-pieces (marked 9 j) and a switch-hole (marked Z) adapted to receive a loop switchplug, (marked D Din Fig. 2,) and when a plug is inserted into a switch-hole its two contactpieces form connection with the two contactpieces 9 and j of the switch, respectively. One side or branch of a line is connected to one contact-piece of each switch of the line say piece gand the other side or branch of the line is connected to the other contactpiece of each switch of the linesay j.

There are two annunciators for each line (marked w w) and two retardation coils for each line, (marked it One side or branch of each line is permanently grounded through one annunciator and retardation-coil of the line, and the other side or branch of the line is permanently grounded through the other annunciator and retardation-coil of the line.

The two annunciators of a line are placed at two boards one at each division of boards and at boards where the calls of the line are to be answered.

Fig. 2 shows an operators cord system for an operator at any board. D D are a pair of Fig. 2 shows the plug.

switch 8 at its board and when so placed to connect its contact-pieces with the two contact-pieces g j of the switch, respectively.

The two contact-pieces of one plug are connected to the two contact-pieces of the other plug, respectively, by two flexible switch-conductors. Each operator has as many pairs of plugs with cords as she may need for her work.

Y is a looping-in switch for the pair of plugs shown, having two switch-levers and three pairs of contact-bolts on which the levers may be alternately placed. The two levers of the switch are connected to the two flexible conductors, respectively, which connect the plugs.

23 is the operators telephone, and O is a testbattery. The telephone and battery are in a loop which connectsa pair of the switch-bolts.

o is a clearing-out annunciator, and O is a test-battery. This annunciator and the battery are in a loop which connects another pair of the switch-bolts.

C is a callinggenerator in a loop, which connects the remaining pair of switch-bolts.

Each pair of plugs has a switch ,Y, a clearing-out annunciator o, and a test-battery O In the operators test system, T is a testplug, and t a test-receiving instrument. The plug is adapted to be placed for testing into connection with any switch-contact g or j at its board and is grounded through the test-receiving instrument. Each operator has a test system.

'In the subscribers station apparatus,(shown in Fig. 4,)1 is the telephone-switch; 2, the subscribers telephone; 3, his signal-bell, and 4 his calling-generator. a and b are two keys each having a pair of contacts normally open, but closed at the will of the subscriber. The circuits and connections are substantially as shown and may be such as are usual in subscribers station apparatus with the addition of the connections of the keys, such as will be described.

When the telephone is on the switch, the signal-bell is in the circuit of the line and the telephone is short-circuited, so as to be practically out of the circuit. When the telephone is off the switch, it is in the circuit of the line and the signal-bell is short-circuited, so as to be practically out of the circuit. The

armature of the calling-generator is in the loop-plugs, each adapted to be placed in any IIO is grounded. The other point of key a is connected to the line-circuit on one side of the generator-armature coil, and the other point of the key 6 is connected to the line-circuit on the other side of the armature.

The subscribers station apparatus should preferably be connected into the line-circuit, so that the generator is between key a and the annunciator of the line which is located in division A of boards and is between key 6 and the annunciator of the line which is located in division B of boards.

The annunciators may all be of the ordinary kind of'nonpolarized telephone-annunciators.

The operation of the system is as follows: If a subscriber wishes connection with a subscriber whose line is in division A, he presses on his key a and operates his generator. A calling-current then goes through a circuit from the subscribers ground through the contacts of key a, the generator, one side or branch of the line, and to ground at the central office through the annunciator located at one'of the boards of division A. The annunciator will thereby indicate a call. The other annunciator of the line will not indicate a call,

because the line is grounded between the; generator and the annunciator by a circuit connection through key a of practically no resistance and the annunciator is practically short-circuited. When the operator to whom the annunciator which indicates the call is assigned observes the indication, she places one of her switch-plugs D in the switch of the line, the levers of the switch Y being in position so that her telephone bridges or cross-connects the conductors of the plug, her telephone is in closed circuit with the line and she will receive the order of the subscriber. This closed circuit is, say, from one side or branch of the line through the plug contact piece connected with it, to the flexible conductor connected with the plug contact-piece, thence to the switch-lever, thence through the telephone to the other switch-lever, thence to the other contact of the plug, and thence to the other side or branch of the line. When the operator receives the order of the subscriber, she tests the line wanted, as will hereinafter be indicated, and ifshe finds itto be free, or not in use, she places the other plug of the pair in the switch of the line. The two lines are then connected together into a closed metallic circuit, and this circuit is bridged or crossconnected by the operators telephone. This closed metallic circuit is, say, from one side or branch of one line to the contact-piece of the plug in its switch, thence through one of the flexible conductors to a contact-piece of the plug, which is in the switch of the other line, thence to one side or branch of the other line, thence through the circuit of that line to the other contact-piece of the plug, which is in its switch, thence through the other flexible conductor to the other contact-piece of the first-mentioned plug, and thence to the other side or branch ofthe first-mentioned line. The operator may now move the lever of the looping-in switch Y, so that the calling-generator B bridges the two sides of the closed metallic circuit, and a calling-current will pass over the metallic circuit to the line of the subscriber wanted and ring his signal-bell. The operator will then move the levers of the switch, so that the clearing-out annunciator o bridges or cross-connects the closed metallic circuit of the two lines. The subscribers will then carry on their conversation. When the subscribers are through conversation, either may operate his calling-generator without pressing on either of his keys at or b. A current will then pass through his metallic circuit, which will operate the clearing-out annunciator in the central ofiice, which bridges pr connects the two sides or branches of his If the subscriber from whom the call had originated had desired conversation with a subscriber whose line is in division B, the operations would have been the same as those described except that he would have pressed on key-b when he sent in his call.

When two lines are connected together into a closed metallic circuit for conversation, one side of the circuit is grounded at the central office through one annunciator and retarda tion-coil of each line and the other side of the circuit is grounded through the other annunciator and retardation-coil of each line. high retardation and resistance of these ground connections or taps are, however, such as not to greatly affect the telephone conversation between the subscribers.

It is evident that when a clearing-out signal is sent by either subscriber, as heretofore described, a portion of the generated current will divide so as to pass through the line-annunciators of the two lines. On account of the high resistance of the circuits through the annunciators the amount of current which passes through them will not be suflicient to operate them. The circuit through the clearing-out annunciator will be of much less resistance, and consequently much more current will pass through it and sufficient to operate it. The strength of the generator and the resistances of the circuits and apparatus and the sensitiveness of the annunciators can be readily adjusted to each other in such a manner that when a call is sent in by a subscriber it will operate the annunciator he intends and will not operate his other annunciator, and when a clearing-out current is sent by either subscriber it will operate the clearing-out annunciator and will not operate either of the lineannunciators.

Should any subscriber attempt to send a call for a connection by pressing either of his keys and operating his calling-generator while his line is already switched for conversation, as

The

together.

may be the case when the subscribers neglect to send a clearing'out signal when they are line-annunciators, and part of the current will also pass through the line-annunciators of the other subscriber if the two lines are connected The greater portion of the current will, however, pass through the clearing-out annunciator. The strength of the generators and the resistances of the circuits and apparatus and thesensitivencss of the annunciator-s can be readily and should be adjusted to each other in such a manner that when a call is sent -in by a subscriber and his line is already switched enough of the current will not pass through any of the line-annunciators to operate them; but sufiicient current will pass through the clearing-out annunciator to operate it. When the operator moves the levers of his switch Y so as to connect her callinggenerator B into circuit, the generator is bridged between the two sides of the combined circuit of the two lines, and the current di vides, according to the well-known law of the distribution of currents in derived circuits, so that the greater part of the current passes in two derived circuits to the two subscribers stations, respectively, and operates their call- -known modifications of the operators switches the line from which the call originates may be disconnected from the generator while the operator sends the calling-current, and in that case the current will only go over the line' and through the annunciators of the subscriber wanted. In either case the strength of the operators generator and the resistances of the circuits and apparatus and the sensi- -tiveness of the bells and the annunciators can be readily and should be adjusted to each other in such a manner that when a call is sent by the operator the line-annunciators will'not be operated, while the subscribers bells (or the subscribers bell, as the case may be) will be rung by the current. The system may be modified-as, for instance, for multiple switchboard systems, which do not contain the divided-exchange featu re by leaving out the annunciator with its ground connection, which is connected to one side or branch of the line. In that case the key of the subscribers station, which is to be depressed to operate this annunciator, may be left out. The line-annunciators, as well as the clearingout annunciator, will be in closed circuit with the generator when the clearing-out signal is 'sent, and in all cases the strength of the ourrent and the resistances of the line-annunciator circuits should be so great as compared with thereslstance-of the clearing-out annunof the line.

ciator-circuit that when the clearing-out current passes through them the line-annunciator will not be operated.

The system of switching and operation which I have herein described may be modified so as to prevent in other ways the lineannunciators from. being operated while the line is switched and either a subscriber or an operator sends a calling-current over the line.

The test system is as follows: When a line is switched for conversation, it has a test-battery, either the battery 0 in the loop with the operators telephone or the battery G in the loop with the clearing-out annunciator, in a bridge or cross connection to the two sides When, therefore, an operator at any board places her test-plugT into contact with any contact-piece g or 1' of a line and the line is switched for conversation, a complete circuit is established which contains her testreceiving instrument and a test-battery, and the instrument will sound or respond, indicating that the line is switched for use. The complete circuit is, say, from ground through the test receiving instrument to the testplug, thence to the switch-contact connected with one side of the line to which the plug is applied, thence to the switch-contact of the line at which the line is switched, thence through the test-battery, which bridges the circuit to the other side of the line, and thence to ground through the annunciator and retardation-coil, through which the last-mentioned side of the line is grounded.

When a line is not switched for conversation, there is no complete circuit established on testing which contains the operators testreceiving instrument and a battery, and the instrument will not sound. The operator can therefore determine by testing whether or not any line connected to her board is switched for conversation.

Instead of the annunciator and retardationcoil for each line an annunciator of high resistance and retardation to telephone-currents may be used.

Other systems of testing than that shown and described may be used in connection with the calling and switching system I have described.

I claim as my invention-- 1. In a telephone-exchange system, the metallic-circuit lines divided into two divisions, the multiple switchboards, divided into two divisions, one division of boards for each division of lines; switches for each of said lines, oneswitch for each line on each of the several boards of its division, and on one board of the other division; two annunciators at the central oflice for each line, through one of which one side or branch of the line is permanently grounded and through the other of which the other side or branch of the line is permanently grounded; in combination with a calling-generator at each subscribers station permanently or whenever operated to send a call in the through or closed circuit of the line at said station, and contacts to at will ground his line on either side of said generator.

2. In a telephone-exchange system, the metallic-circuit lines divided into two divisions, the multiple switchboards divided into two divisions, one division of boards for each division of lines, switches for saidlines, one switch for each line on each board of its division and on one board only of the other division, each switch having two contactpieces, one branch of each line being connected to one of the contact-pieces of each switch of the line and the other branch of the line being connected to the other contact-piece of each switch of the line, in combination with two permanent ground connections at the central office for each line, two annunciators for each line, one in each of the ground connections and at a board in each division of boards and Where the line has a switch, pairs of loop switch-plugs at each board, the two contacts of each plug being connected by flexible conductor-circuits to the two contacts of its mate, respectively, each plug being adapted to be inserted into each switch at its board and when inserted to form contact between its two contacts and the two contact-pieces of the switch, respectively, a calling-generator at each subscribers station permanently or whenever operated to send a call in the through or closed circuit of the line at said station, and contacts at each subscribers station to at will ground the line on either side of the generator.

3. In a telephone-exchange system, the metallic-circuit lines divided into two divisions, the multiple switchboards divided into two divisions. one division of boards for each division of lines, switches for said lines, one switch for each line on each board of its division and on one board only of the other division, each switch having two contact-pieces, one branch of each line being connected to one of the contact-pieces of each switch of the line and the other branch of the line being connected to the other contact-piece of each switch of the line, in combination with two permanent ground connections at the central office for each line, two annunciators for each line, one in each of the ground connections and at a board in each division of boards and where the line has a switch, pairs of loop SWltClP send a call in the through or closed circuit of the line at said station, and contacts at each subscribers station to at will ground the line on either side of the generator.

4. In a telephoneexchange system, a metallic-circuit line extending from its subscribers station to the central oflice, and two annunciators at the central oflice for such line, through one of which one side or branch of the line is permanently grounded, and through the other of which the other side or branch of the line is permanently grounded, in combination with a calling-generator permanently or whenever operated to send a call in the through or closed circuit of the line at the subscribers station and two keys there, each with a pair of contacts normally open but closed at the will of the subscriber, one contact of each key being grounded and the other two contacts of the keys being connected to the line-circuit, one on one side and the other on the other side of the generator.

5. In a telephone-exchange system,metalliccircuit lines extending from the subscribers station to the central oflice, and two annunciators at the central office for each line, through one of which one side or branch of the line is grounded and through the other of which the other side or branch of the line is grounded, in combination with a calling-generator permanently or whenever operated to send acall in the through or closed circuitof the line at the subscribers station, two keys there, each with a pair of contacts normally open but closed at the will of the subscriber, one contact of each key being grounded .and the other two contacts of the keys being permanently connected to the line-circuit, one on one side and the other on the other side of the generator, and switching apparatus at the central oflice to connect together any two of the lines into a metallic circuit which does not contain the line-annunciator.

6. In a telephone-exchange system, two metallic-circuit lines temporarily connected together into a closed metallic circuit for conversation, and two annunciators for each line, through which, respectively, the two sides of said metallic circuit are grounded in four ground connections, two from each side of the circuit, in combination with a clearingout annunciator in a bridge or cross-connecting circuit to said closed metallic circuit, and

a calling-generator operated in said circuit at either subscribers station to send a clearingout signal, the strength of thegenerator, the resistances of the various apparatus, and circuits, and the sensitiveness of the annunciators being such that when the generator is thus operated, the line-annunciators will not be operated while the clearing-out annunciator will be operated by the current passing through them.

7. In a telephone-exchange system, two metallic-circuit lines temporarily connected together into a closed metallic circuit for conversation, and two annunciators for each line, through which, respectively, the two sides of said metallic circuit are grounded in four ground connections, two from each side of the circuit, in combination with a clearingout annunciator in a bridgeor cross-connecting circuit to said closed metallic circuit, and a calling-generator operated in said oircuit'at either subscribers station to send a clearingout signal, said line-annunciators not being operated but said clearing-out annunciator being operated by the current generated.

8. In atelephone-exchange system, two metallic-circuit lines temporarily connected together into a closed metallic circuit for conversation, and four annunciators through which, respectively, the two sides of said metallic circuit are grounded in four ground connections, two from each side of the circuit, in combination with a clearing-out annunciator in a bridge or cross-connecting circuit to said closed metallic circuit, and a calling-generator operated in said circuit at either subscribers station to send a clearing out signal, the strength of the generator, the resistances of the various apparatus and circuits, and the sensitiveness of the annunciators being such that when the generator is thus operated, the line-annunciators will not be operated while the clearing-out annunciator will be operated by the current passing through them.

9. In a telephone-exchange system, two metallic-circuit lines temporarily connected together into a closed metallic circuit for conversation, and four annunciators through which, respectively, the two sides of said metallic circuit are grounded in four ground connections, two from each side of the circuit, .in combination with a clearing-out annunciator in a bridge or cross-connecting circuit to said closed metallic circuit, and a calling-generator operated in said circuit at either subscribers station to send a clearing-out signal, said lineannunciators not being operated, but said clearing-out annunciator being operated by the current generated.

10. In a telephone-exchange system,two metallic-circuit lines temporarily connected together into a closed metallic circuit for conversation, and two annunciators for each line, through which, respectively, the two sides of said metallic circuit are grounded in four ground connections, two from each side of the circuit, in combination with a clearing-out annunciator, in abridge or cross-connecting circuit to said closed metallic circuit, a calling-generator operated in said circuit at either subscribers station and a key then operating to ground said circuit at said station on one side of said generator, the strength of the generator, the resistances of the various apparatus and circuits, and the sensitiveness of the annunciators being such that when the generator is thus operated, the line-annunciators will not be operated while the clearingout annunciator will be operated by the current passing through them.

11. In atelephone-exchange system,twometallic-circuit lines temporarily connected together into a closed metallic circuit for conversation, and two annunciators for each line, through which, respectively the two sides of said metallic circuit are grounded in four ground connections, two from each side of the circuit,.in combination with a clearingout annunciator in a bridge or cross-connecting circuit to said closed metallic circuit, a calling-generator operated in said circuit at either subscribers station and a key then operating to ground said circuit at said station on one side of said generator, said line-annunciators not being operated but said clearing-out annunciator being operated by the current generated.

12. In atelephone-exchange system,two metallic-circuit lines temporarily connected together into a closed metallic circuit for conversation, and two annunciators, through which, respectively, the two sides of said metallic circuit are grounded, in combination with a clearing-out annunciator in a bridge or crossconnecting circuit to said closed metallic circuit, a calling-generator operated in said closed metallic circuit at either subscribers station and a key then or while the generator is thus being operated in said closed metallic circuit operating to ground said circuit at said station on one side of said generator, said line-annunciators not being operated but said clearing-out annunciator being operated by the current generated.

13. In a telephone-exchange system,two metallic-circuit lines temporarily connected together into a closed metallic circuit for conversation and a line-annunciator through which one side of said metallic circuit is then grounded in combination with a clearing-out annunciator in a bridge or cross-connecting circuit to said closed metallic circuit, a calling-generator operated in said closed metallic circuit at either subscribers station to send a clearing-out signal, and a key then or while the generator is thus being operated in said closed metallic circuit operating to ground said circuit at said station on one side of said generator and with said generator between said ground connection thus established and said annunciator, the strength of the generator, the resistances of the various apparatus and circuits, and the sensitiveness of the annunciators being such that when the generator is thus operated the line-annunciator will not be operated, while the clearing-out annunciator will be operated by the current passing through them.

14:. In a telephone-exchange system,two metallic-circuit lines temporarily connected together into a closed metallic circuit for conversation and a line-annunciator through which one side of said metallic circuit is then grounded, in combination with a clearing-out annunciator in a bridge or cross-connecting circuit to said closed metallic circuit, a calling-generator operated in said closed metallic circuit at either subscribers station to send a clearing-out signal, and a key then or while the generator is thus being operated in said closed metallic circuit operating to ground said circuit at said station on one side of said generator and with said generator between said ground connection thus established and said annunciator, said line-annunciator not being operated but said clearing-out annuncialor being operated by the current generate In testimony whereof I have hereunto subscribed my name.

MILO G. KELLOGG. Witnesses:

H. M. WALKER, E S. WALKER.

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