US2007990A - Signal telephone system - Google Patents

Description

July 16, 1935,

w. H. WAITE SIGNAL TELEPHONE SYSTEM Filed April' 1, 1933 2 Shets-Sheet 1 INVENTQR AX W July 16, 1935. 0 w, w E 2,007,990

S IGNAL TELEPHONE SYSTEM Fild April '1, 1953 2 Sheets-Sheet 2 3 [A /0' V 56 a 8? Em I Q \IMI 67 g 6 60 6 20 6f 92 INVENTOR 'ATTORNEYS Palm-.1 July 1c, 1935 I .JNITED STATES PATENT OFFICE This invention relates to a signal telephone system especially adapted for use in hospitals,

although the invention 'is not limited to this use. A telephone system of this type is disclosed in 5 my prior Patent No. 1,841,771, dated January 19,

rality of substations connected to the master station and located in the various patients private rooms, adjacent the beds of patients in wards, or the like, and corresponding signal devices, such as lights or audible signals are located at the master station corresponding to the several substations, over or adjacent to the doors of the patients private rooms, over or adjacent the beds or the patients in the wards, on their instruments, or the like, and pilot signals, preferably visual, are located at the heads of corridors, over the doors" of the wards, or the like, to indicate that a patient in that particular corridor or in that particular ward is signaling. The improvement of the present invention resides principally in the arrangement of the circuits whereby the amount of necessary wiring is. reduced to such a degree that the existing annunciator wiring in a hospital may be used without substantial change, and the former annunciator system converted into a telephonic system. For example, in the system of the aforementioned patent there are two individual wires for each substation and three common wires, whereas in the new system of the presentinvention thereis only oneindividual wire for each substation and tour common wires. Accordingly, in a typical installation having twenty substations, the system of the patent requires 43 wires and the new system of this invention requires only '24 wires, or approximately of the total wiring, which considerably reduces the cost and size of the main cables,'simplifics the installation of the system in new and existing hospitals, and permits the use of existing annunciator cable without substantial change in so far as the number of wires is concerned. a v

In the preferred embodiment of the invention, actuation of a substation signal button by a patient energizes a corresponding signal at the master station in the nurses or central oflice and the pilot and door signals, and prepares the talking circuit for establishment by the nurse responding at the master station. In responding to the signal, the nurse actuates a corresponding key, switch, or the equivalent, which deenergizes the master station and pilot signals and establishes the telephonic circuits between the nurse's and the patients telephone-instruments and the circuit is ready for communication between the nurse-and the patient in response to the patients original signal. Restoration of the nurse's switch opens the talking circuit, but the signals are maintained until the patients button is released, which is locked in closed position after manipulation, so that the signals remain until responded to. An auxiliary audible signal is also preferably provided at the master station to call attention to a calling patient, but the signal does not remain energized when the button is locked closed, althoughit is energized each time the patient presses the locked button.

In a modified arrangementsof the system of the present invention, the nurse at the master station, by throwing a switch, completes her talking circuit from her transmitter to the patients loud speaker, so that the nurse may talk to the patient at any time and the patient mayrespondu,

by pressing the corresponding button to complete the patients talking circuit between the patients transmitter and the nurse's receiver. This paging feature is a. valuable adjunct in a hospital signaling system, for the reason that with it a supervisor may communicate with any and all of the patients in a short time without making many personal trips to the patients private rooms or to the 'wards in accordance with the usual practice.

It will be seen that the present invention has all of the advantages of facilitated communication between the several patients and the nurse, I

which are incorporated in the system of the aforementioned patent, and has the additional advantages of simpler wiring, the paging feature,

and other advantages which will be ascertained upon reference to the accompanying drawings,

Referring to Figure 1 of these drawings, letters A. B. C, D, E and F designate the substations in the various patients private rooms in a hospital, or the several beds in a ward which is equipped with the substations mentioned. The letter M designates the master station in the nurses office to which the several substations are connected.

- The master station M in the nurses" office is equipped with a plurality of switches, keys, or the like, designated a, b, c, d, e and 1, corresponding to thesubstations A, B, C, D, E and F, respectively, The master station M is also equipped with the visual signals al, bl, cl,- dl, el, and fl, individual to the keys a, b, c, d, e and f, and corresponding to the substations A, B, C, D, E and F, respectively. These visual signals may be shutters or flags, as indicated, signal lights, or the equivalent, and are so arranged that when a flag is raised or a light illuminated it identifies visually the substation which is calling.

Each of the substations A, B, C, D, E and F is provided with a corresponding visual signal Al, Bl, Cl, DI, El, and Fl, which are located over or adjacent the .doors of the corresponding patients private rooms, over or adjacent the corresponding bed or on the instrument in the ward, or the like.

Also, located at the head of a corridor, wing, or section of patients private rooms over or adjacent the door of a ward, or the like, is a visual signal in the form of a pilot lamp P, which indicates that a patient in that corridor or wing, section, ward, or the like, is signaling, and a nurse may then identify the particular patient who is signaling by his or her private lamp Al, Bl, Cl, Dl, El, or Fl. As indicated in Figure 1, one of the pilot lamps PI is individual to substations A, C, E, and the other pilotlamp P2 is individual to substations B, D, E, which in the particular arrangement illustrated, may be the way in which the private rooms are divided by the corridors, wings, or sections, or the way in which the substations are classified or arranged in wards, or the like.

The substations A, B, C, D, E and F are all alike and therefore the description of one of them, namely, substation A, will suffice for all. The substation includes a patients receiver Ill, which is preferably a loud speaker, a patients transmitter H, which is preferably a microphone, and a push button l2, which the patient depresses when he wishes to speak to the nurse at the nurses oflice. be mounted in or on a portable casing standing adjacent the patients bed, or the like, and the push button may be conveniently placed at the end of a flexible cord so as to be available to the patient. The push button l2 locks in closed position afterbeing pressed and remains in closed position until it is released. Any suitable type of locking button may be employed and for purposes of illustration a diagrammatic form of locking button is disclosed. This button includes a first contact II which is provided with an extension which hooks under the abutment of a latch l4, so that the spring contact I3 is held down after the button I2 is pressed. Below the first spring contact I8 is a second spring contact l5, adapted to be engaged by first spring contact I 3 and remain eng ged therewith while latch i4 holds first contact i 3 in closed position. Similarly, below second spring contact I5 is a third spring contact I, adapted to engage therewith; below third spring contact I is a fourth spring contact l1, adapted to engage with the former,v and below the fourth The instruments enumerated may spring contact I1 is a fifth spring contact ll, adapted to engage with the former. The fifth spring contact l8, however, does not remain engaged with fourth spring contact I! when the first spring contact I3 is held locked in closed position by latch l4, although all of the other spring contacts are in mutual engagement. Fifth spring contact I8 is only engaged with. fourth spring contact l1 when the button l2'is depressed below the point at which the latch l4 engages it. Thus,

when the patient presses. button l2 all of the spring contacts, including fifth spring contact it are in engagement, but when the patient releases pressure on button l2, fourth spring contact ll becomes disengaged from fifth spring contact. it, although the latch holds the first, second, third and fourth spring contacts l3, l5, l6 and I1, respectively, in engagement. The purpose of this arrangement will be described later.

First spring contact I3 is connected by wire I! to a contact 20 normally engaged with armature 2i of relay 22, and armature 2| is in series with patients microphone II, which is connected by wire 23 to the talking wire 24 of the main cable of the system.

The second spring contact I5 is connected by wire 26 to relay22, the other terminal of which is connected by wire 21 to switch contact 28 of key a, and this contact is normally engaged with contact 29 connected by wire 30 to the relay 3| of signal flag al, and the other terminal of this relay is connected to wire 32, which in turn is connected to the positive line wire 33 of the main cable, which is connected to-the corresponding pole of signal battery 34, the negative terminal of which is connected to negative line wire 35 of the main cable. The patients loud speaker Ill is connected in parallel with the relay 22 and one of the leads of the loud speaker l0 contains the condenser 36, the purpose of which will bedescribed later. The armature 31 of fi relay 3| is adapted to engage spring contact 3 when the-relay 3i is energized to close a circuit leading from positive line wire 33, wire 32, spring contact 38, armature 3l of flag relay 3i, wires and 4|, pilot lamp Pi and negative line wire 35.

The third spring contact l8 of the patients push button switch is connected by wire 42 to the corresponding door, bed or instrument lamp Al,

which is connected by wire 43 to positive line wire 33.

The fourth spring contact I! of the patients push button switch is the negative feed forthe push button and is connected by wire 44 to negative line wire 35.

The fifth spring contact l8 of the patients push button switch is connected by wire 46 to line wire 41, which is the audible signal wire of the main cable and is connected by wire 41' to the audible signal 43 at the master station, which may be in the form of a buzzer, or the like, the other side of which is connected through disconnect switch 49 by wire 50 to the positive line wire 33. The use of the buzzer 48 depends upon requirements, and it may be omitted if not required and thus one of the line wires of the main cable will be eliminated, namely, wire 41.

Each of the other substations B, C, D, E and F, is provided with an individual wire 21 corresponding to wire 21 to substation A, this wire being connected to the corresponding key at the master station, and the other wires 23', 44' and 46 leading from the remaining substations, B,

C, D, E and F, correspond to wires 23, "and" of the substation A just described.

Spring contact 5| cooperating with common contact 28 of nurses station key a, which is normally disengaged from common contact 28, is connected by wire 52 to the nurses transmitter 53, the other pole of which is connected by wire 54 to spring contact 55, adapted to engage contact 56, which is connected by wire 51 to the positive terminal of talking battery 58, the negative pole of which is connected to negative line wire 35 of the main cable.

Joined to spring contact 55 of nurses key a by an insulating block 55, so as to move therewith, is a second spring contact 60, which is connected by wire 6| to wire 24 of the main cable and which is adapted to engage spring contact 62 which is connected by wire 63 to nurses receiver 64, the other terminal of which is connected to the positive pole of talking battery 58 through resistance 65. A second resistance 65 is connected across the terminals of the nurses receiver 54. A talking impedance coil 61 is interposed between negative line wire 35 and nurses microphone 53.

The telephonic circuit just described is shown in the simplified schematic diagram of Figure 2 in which the winding of relay 22 is represented as an impedance across the terminals of the patients loud speaker Ill. The connections of the switch, telephonic instruments and signal devices corresponding to other substations are identical to those described in connection with substation A and therefore they need not be further described.

In operation, assuming that the patient at substation A presses push button l2 to signal a nurse at the central oflice, several circuits are completed,

one of which includes the buzzer 48' in the central omce, this circuit being traceable from signal battery 34, by positive line wire 33, wire 50, buzzer disconnect switch 49, buzzer 48, wire 47', buzzer line wire 41, wire 46, fifth push button spring contact it, fourth push button spring contact I'l, wire 44, negative line wire 35 and back to battery 34. When theLpatient releases pressure on push button i2 the fourth spring, contact H disengages fifth buzzer spring contact it to denergize the buzzer 48, but the remaining spring contacts remain mutually engaged because latch It holds themin engagement in the manner 11- lustrated in Figure 1. Subsequent pressure by the patient on button l2 reenergizes buzzer 48 for as long a period of time as thepatient maintains the button 12 depressed. If the patient presses the push button l2 insistently, the nurse may silence the buzzer by opening the disconnect switch 49.

Engagement between third and fourth push button contacts I6 and II, respectively, establishes a circuit from negative contact ll, contact l6, wire 42, door lamp AI, and positive line wire 33. The door lamp Al over the door of the private room of the patient ,who signaled is accordingly illuminated to indicate tothe nurse which patient is calling, if the nurse happens to be out of her office, it being understood that the lamp AI may be over the bed of a calling patient in the ward, or the like.

Engagement between second and third contacts l5 and I5, respectively, establishes a circuit from negative contact I! through contact l6, contact l5, wire 25, relay 22, wire 21, closed contacts 28 and 29 of key a at the nurses station M, wire 33, relay 3|, wire 32 and positive line wire 33. Energization of relay 22 breaks the normal circuit of the patients transmitter or microphone I l by disengaging armature 2| from contact 20. Since this action takes place substantially simultaneously with the closing of the circuit of the patients transmitter or microphone H by manipulation of the patients push button l2, the patients talking circuit practically remains deenergized.

Energization oi flag relay 3| causes it to attract its'armature 31 and raise flag or shutter at to designate to the nurse at the master station M that the patient at substation A is signaling. At the same time armature 3! engages contact 33 to close a circuit from negative line wire 35, pilot light Pl, wire 45, contacts 3! and 38, wire 32, and positive line wire The illumination of pilot lamp Pl indicates to a nurse, if she is not in her office, that a patient in the corresponding corridor, wing, ward, or section of the hospital is calling and she may then, by glancing at the door or bed lamps All, Ci, and El, ascertain which of the patients is calling, it being the patient at substation Al in this particular instance.

At the master station M the nurse, having been notified by the sounding of buzzer 48 that a pa tient is calling, glances at the master station instrument and identifies the patient because of the display of flag or shutter at. She then manipulates the key a, which breaks the normal connection between contacts 28 and 29 and makes contact between contacts 23 and 5!, 55 and 5t, and 63 and 52. The disengagement of contacts 26 and 29 deenergizes flag relay 3i so that flag a drops to break the contact between armature 31 and contact 33 and extinguish pilot lamp Pi. The disengagement of contacts 28 and 29 also deenergizes relay 22, which accordingly releases its armature it so that the latter reengages contact 20 to remake the circuit of patients transmitter or microphone H, which is traceable from negative contact ll, contacts it, I and I3, wire l9, contacts 25 and 2 l transmitter or microphone H, wire 23, line wire 25, wire ti, contacts 65 and 52 of key a, wire 53, nurses master station receiver 5d, resistance 65, wire 5? to talking battery 58, thus establishing the patients talking circuit.

Engagement between contacts 55 and 55 and of contacts 28 and 5i of key a establishes two circuits, one traceable from talking battery 55 through wire 51, .contacts 56 and 55, wire 55, transmitter 53, wire 52, impedance 6i, line wire 35 back to' talking battery 58 and a circuit in shunt with impedance 5! traceable through wire 52, contacts 5! and 28, wire 23, loudspeaker l3 and blocking condenser 36 shunted by relay 2?, wire 25 contacts l5, l5, l1, wire 45, line wire 35. Although relay 22 is now in the energized circuit of talking battery 58 the voltage applied to relay 22 is insuflicient to operate it so that armature 2| and contact 20 remain in engagement. The patients listening circuit is accordingly established and communication between the patient and the nurse at the master station may As indicated in the schematic diagram of Fig denser I0 servesto shunt, current from signal battery 34 through patients relay 22 when the patients pushbutton I2 is pressed, thus energizing relay 22. The patients relay22 renders the system selective, for it this. relay were not preseat, all microphones of the other patients substations whose pushbuttons were operated would be connected to the nurse's receiver, so that the latter could hear any noises in the rooms of the other patients. Upon completion of the conversation between the patient and the nurse, the latter restores key a to its initial position. which disconnects the circuits to the nurse's transmitter 52 and receiver 54 and, by the reclosure of contacts 28 and 29, patients relay 22 and flag relay ii are reenergized separating armature 2i from contact 20 on patients relay 22 and reenergizing pilot lamp Pl through the closing of contacts 21 and 28 on flag relay 3i, unless the patient has reopened the locking button in the meantime by releasing the latch i4, whereupon all circuits are reopened including the circuit of relay 22, which accordingly releases armature 2| to reengage contact 20 and prepare the normal circuit through patients transmitter or microphone II for completion by subsequent manipulation of the patients button i2. The door lamp AI and the corresponding pilot lamp Pi are also extinguished when their corresponding contacts l6 and 31-48, respectively, are open. The system is now restored to its original condition for reoperation by any one of the substations in the manner described.

Incorporation of the paging features, whereby the nurse at the master station may talk to the patient at any time without awaiting a signal from the patient, is simply made by changing the connections of the patients loud speaker III. Instead of connecting the patients loud speaker [0 directly in-parallel with the relay 22, as in the arrangement illustrated in Figure 1, it is bridged across wires 21 and 44, as illustrated in Figure 3. With this arrangement the nurse at the master station simply throws key a to establish two circuits, one from talking battery 52 through wire 51, closed contacts 56 and II, wire N, master station transmitter 52, impedance 61', wire 25 back to talking battery 58, and the other from impedance 61 through wire 52, key contacts II and 22, wires 21 and I0, patients loud speaker ll, blocking condenser 36, and wires Ii, 44 and II, back to they other side of impedance 8! thus establishing a talking circuit between the nurse's transmitter i2 and the patients loud speaker M without any previous preparation of the circuit by the patient or the display of signals.

Manipulation of the nurse's key also prepares the patients talking circuit to the nurse's receiver 84 from talking battery ll, resistance 8!, receiver M, wire 63, key contacts 62 and 60, wires I, 24 and 22, patients microphone ll, closed contacts 2| and 20, wire i9, and open contacts is, ii, I and II. This circuit, 1. e., the patients talking circuit, may be completed by the patient upon manipulation of his button i2 in the manner described.

Manipulation of the patients button l2 does not, in this instance. break the circuit to the patients microphone ll because relay 22 remains deenergized.. due to the disconnection between key contacts 20 and 2. resulting from manipul s' tion of the nurse's key. a.

In this waya nurse at the master station may page all of the patients without making it necessary for the nurse tomake personal trips to the various patients rooms. This is a valuable ad'- junct to a hospital communication system. since in many instances it is desirable for the nurse to locate a doctor or to communicate with the patient without leaving the nurse's station.

accordance with the present invention without disturbing the annunciator cables in any way except to make connections at the open ends thereof. This arrangement is illustrated diagrammatically in Figure 4, in which the original annunciator i2 iltted with signals such as lamps A2, B2, C2, D2, E2 and F2,-corresponding to the patients rooms, beds, or the like, A, B, C, D, E and F, respectively, is employed instead of the flag signals al at the master station. These lamps or other signals are connected in the circuits of the nurses corresponding keys to take the place of the flags al, illustrated in the arrangement of Figure 1. For example, the contact 2! of each of the nurse's keys a, b, c, d, e and I is connected to the corresponding lamp or other signal of the annunciator 12, the remaining connections of the circuit being the same as illustrated in Figure l and may include the buzzer 48, although this audible signal is not shown in Figure 4.

With this arrangement, manipulation of the patientsbutton l2 at substation A, for example, closes a circuit from positive line wire 32 to the annunciator 12 through wire 12, annunciator lamp or other signal A2, wire 30', normally engaged contacts 29 and 28 of master station key switch a, wire 21, substation relay 22 and patients loud speaker I0, wire 28, patients button second contact i5, third contact l8, fourth contact I'l, wire 44 and negative line wire 3!. The resultant energization of annunciator signal A2 identifies the calling patient at substation A, and the nurse responds as before, by manipulating corresponding key a at the master station.

It will be seen that annunciator wire's take the place of'line wires 24, 22 and I1 and the individual substation wires 21, and since, the annunciator wires are already installed in existing cables of the hospital, rewiring of the hospital becomes unnecessary, and the attendant labor, noise, and excavation of the walls or floors of the hospital to lay the line wires or cables are eliminated.

It will be seen that the new telephone signal system of this invention, although extremely simple and employing a minimum number of wires and other parts, is nevertheless absolutely selective, whereby communications between the master station and the individual patients remain private. with the paging feature the nurse at the master station may throw the key corresponding to the patient to whom she wishes to speak and talk to the patient at any time and the patient may answer by pressing the button l2 and talking.

While the system of the present invention has been illustrated and described as being particularly adapted for use in hospitals. it is to be understood that its utility is not limited to this purpose, but the system may be employed wherever an intercommunicating telephone system of simple construction is desired. .Also, while a preferred embodiment of the invention has been illustrated, it is also to be understood that the invention is not limited thereby, but is susceptible to changes of form and detail within the scope of the claims.

I claim:

1. In atelephone system, the combination of a master station'having a telephone instrument, a plurality of substations each having a telephone instrument, a plurality of common conductors each connected to said substation and to the master station, and only one wire between each substation instrument and the master station instrument which'is individual only to those instruments.

2. In a telephone system, the combination of a master station having a telephone instrument, a plurality of substations each having a telephone instrument, a plurality of common conductors each connected to each substation and to the master station, only' one wire between each substation instrument and the master station instrument which is individual only to those instruments, and a switch in each single wire for connecting and disconnecting the corresponding substation instrument with the master station instrument.

3. In a telephone system, the combination of a master station having a telephone instrument, a plurality of substations each having a telephone instrument, apluralityof common conductors each connected to each substation and to the master station, only one wire between each substation instrument and the master station instrument which is individual only to those instruments, and a switch at the master station corresponding to each substation and connected in the single wire thereof for connecting and disconnecting the corresponding substation instrument with the master station instrument.

. f1. In a telephone system, the combination of a master station having a telephone instrument, a plurality of substations each having a telephone instrument, a plurality of common conductors each connected to each substation and tothe master station, only one wire between each substation instrument and the master station in-- strument which is individual only to those instruments, and a switch at each substation con-- nectedin the single wire thereof for connecting and disconnecting the corresponding substation instrument with the master station instrument.

5. In a. telephone system, the combination of a master station having-a telephone instrument a plurality of substations each having a telephone instrument, a plurality'of common conductors each connected to each substation and to the master station, only one wire, between each substation instrument and the master station instrument which is individual only to those instruments, a switch at the master station corresponding to each substation and connected in the single wire thereof, and a switch at each substation connected in the single wire thereof, the master station and substation switches being adapted to connect and disconnectthe corresponding substation instruments with the master station instrument.

6. In a telephone system, master station having a telephone instrument, a plurality of substations each having a telephone instrument; a plurality of common conductors each connected to" each substation and to the a master station, one wire between each substation instrument and the master station instrument which is individual only to those instruments, a relay in the single wire of each substation, a. second telephone responding relay.

plural "f we: substations each. having a telephme instrument, a plurality OI'OQIBIXIOD conductorsand to the each connected to each substation cone telephone-instrument, and the combination of a Y instrument at each substation controlled by the corresponding relay, and a, switch in each single wire for operating the cor-.

Vmaster station having atelephone instrument, a

which is individual only to those instruments, 9.

relay in the single wire of each substation; a sec-' ond telephone instrument at each substation controlled by the corresponding relay, and a switch at the master station for operating the corresponding relay.

r 8. In a telephone system, the combination of a master station having a telephone instrument, a. plurality of substations each having a telephone instrument, a plurality of common conductors each connected to each substation and to the master station, one wire between each substation instrument and the master station instrument which is individual only to those instruments, a relay in the single wire of each substation, a. second telephone instrument at each substation controlled by the corresponding relay, and a switch at each substation ioroperating the corresponding relay.

9. In a telephone system, the combination of a master station having a telephone instrument, a plurality of substations each having a telephone instrument, a plurality. of common conductors each' connected to each substation and to the master station, one wire between each substation instrument and the master station instrument which is individual only to those instruments, a relay in the single wire of each substation, a second telephone instrument at each substation con- 1 to the master station, one wire between each substation instrument and the master station instrument which is individual only to those instruments, a relay in the single wire of each substation, a second telephone instrument at each substation controlled by' the corresponding relay, a switch in each single wire for operating the corresponding relay, and a second telephone instrument at the master station connectible to the second instrumeninat a substation upon operation'of the corresponding switch.

11. In; a telephone system, the combination of a master station having a telephone instrument, a substation having a telephone instrument, a normally closed circuit for at least one of said telephone instruments, a switch at the substation for breaking the normally closed circuit of said a switch at the master station for restoring the circuit of said one telephone instrument and establishing a talking circuit between the master and said substation instruments.

12. In a telephone system, the a master station having a telephone instrument, a plurality of substations each having a telephone instrument, a normally closed circuit for each substation instrument, a switch for breaking the normally closed circuit of the instrument at one of the substations, and storing the circuit of the instrument at the said one substation and establishing a talking circuit between themaster and said substation instru-- ments. V

'13. In a telephone system, thecombination of a master station having atelephone instrument, -aplurality of substations combination of a second switch for reeach. having a tele- 1'6 6 aoo'moo phone instrument, a normally closed circuit for each substation instrument, a switch at each substation ior breaking the normally closed circuit of the corresponding telephone instrument,

and a second switch at the master station for restoring the circuit of the instrument at the said one substation and establishing a talking circuit between the master and said substation instruments.

14. In a telephone system, the combination of a master station having telephone instruments, a plurality of substations having telephone instruments, a normally closed circuit for each substation instrument, a switch at each substation for breaking the normal circuit of at least one of the corresponding substation instruments, and a switch at the master station for restoring the normal circuit of said one substation instrument'and establishing a communication circuit between the said master station and substation instrument.

15. In a telephone system, the combination of e a master station having telephone instruments,

.a plurality oi substations having telephone instruments, a switch at the master station tor establishing a communication circuit only between the master station transmitter and a substation receiver, a second switch at the master station for preparing a second communication circuit between the master station receiver and the transmitter of the said substation, and a switch at the said substation for completing the said second communication circuit.

17. In a telephone system, the combination of remote stations each having telephone instru ments, a switch at one station for establishing a communication circuit between one of the instruments thereof and the corresponding instrument at another station, a second switch at said one station for preparing a. commlmication circuit between the other instrument thereof and the corresponding instrument at said other station, and a switch at the said other station for completing at will the said second communication circuit.

18. In a telephone system, the combination of a master station having telephone instruments, a plurality of substations each having telephone instruments, a switch at each substation for preparing a communication circuit to the master station, a switch at the master station for completing the said communication circuit to the corresponding substation, a second switch at the master station for preparing a second communication circuit to the last-named substatiomand a second switch at the said last-named substation for completing the second commtmicatloncircuit.

wnnmnwarrn.

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