Patent GB-1080808-A (GB)
Title: Telephone systems
Inventor: TRUBY RALPH
IPC: H04M11/02
Filed: 1965-01-27
Abstract: 1,080,808. Direct call systems. WESTERN ELECTRIC CO. Inc. Jan. 27, 1965 [Jan. 30, 1964], No. 3520/65. Heading H4K. A connection between a master-station and a sub-station in a direct-call intercommunication system using microphone and loud-speaker may be transferred to the substation's private exchange wire, in order to use the substation hand-set for privacy, but without going through the private exchange. An arrangement is described in which a nurse at a master station initially communicates to patients in a ward via individual patient microphones and loudspeakers, the patients can then transfer the call to the patient handset. The Figures, which are arranged as shown in Fig. 9, show a nurse master station (Fig. 2), a patient station (Fig. 3) and control equipment (Figs. 4 and 5), the equipment shown in Fig. 4 is repeated for each additional patient station. Patient station (Fig. 3). The patient communicates to the nurse on the direct call system by means of his microphone M and loud-speaker S, via the intercommunication channel PIC1 and may transfer to the private exchange wires PTC1 by lifting the handset PHS1. The switch-hook contacts initiating the switching of the private exchange wires from the exchange directly to the nurse communication channel. A nurse call key NCK1 operator visual and audible signals to alert the nurse which may be cancelled by switch NCRK1. Nurse station (Fig. 2). The nurse always communicates with the patients via the handset NHS1 connected to the common equipment by communication channel NIC through intercom key IPK1. The line pick-up key LPK1 connects the handset directly to the exchange 104 although the ringer NR1 is always connected to the exchange. The nurse can only speak to a patient station by operating one of the selection keys SSK1 . . . SSK60 either to initiate a call or to answer a call from a patient in which case the appropriate station lamp SL1 . . . SL60 flashes. If the nurse is absent, patient to nurse calls are transferred to a remote station RHS1 by key RTK1 and if more than one patient is calling a preference lock-out circuit in the common equipment connects them to the remote station one at a time. Common control equipment (Figs. 4 and 5). The equipment shown in Fig. 4 is individual to the patient station shown in Fig. 3 and effects the switching of the channels and controls the visible and audible signals at the patient and nurse stations. The equipment shown in Fig. 5 is common to all patient stations, the interrupter supplying the signal potentials and the voice switching control unit 5VSCU joining the two wire speech channel NIC from the nurse to the four-wire direct-call channel PIC1 of the patient station. Patient to nurse call. The momentary operation of the nurse-call key, say NCK1 initiates various visible and audible signals to alert the nurse. Transistor 4T3 initially comes on due to the application of ground to its emitter by NCK1 over lead 309 and completes an operating circuit for relay 4NC, which then locks up through the transistor and make contacts 4NC-2 and the break contacts 4P1-1 and 4P2-1 to ground. Relay 5ST now operates and by closing contacts 5ST-4 energizes the interrupter which supplies 60 i.p.m. ground potential to lead 508 to energize transistor 4T4 and flash the door lamp, and 60 i.p.m. potential on lead 506 to flash the patient lamp PL1 and individual patient station lamp SL1 at the nurse station, and the 60 i.p.m. potential on leads 503, 217 sounds the buzzer. The nurse is thus alerted and answers by lifting the handset and operating intercom key IPK1, so applying ground to leads 224, 203 to bring on relay 5N1 and subsequently relays 5T1 and 5WT. The output of a tone source is then applied through the make contacts 5WT-1 to the nurse communication channel and with the A.C. potential LB applied to the nurse station lamp LL1 through the now closed contacts 5N1-3 indicates to the nurse that a patient station may be selected. Momentary operation of a patient station key, say SSK1, where the lamp is flashing, applies ground to leads 401, 505 so operating relay 5S, which locks on over its contacts 5S1-1. The capacitor associated with the transistor 5T2 previously turned on when the nurse handset was lifted, now begins to discharge, drawing current through resistor 5R1 the potential across which rises and turns transistor 5T2 off and removes the operating circuit for relay 5N2. The release of this relay opens the operating and locking circuit of the - P1 relay of each patient station at the make contact 5N2-4. Any previously connected patients are thereby disconnected. When the capacitor has discharged negative potential is again applied to the base of transistor 5T2 which comes on again. The ground potential on lead 401 from SSK1 also operates the 4P1 relay which is locked over make contacts 4P-1 and break contacts 4P2-1. The relay 4P1 connects the patient communication channel P1C1 to the voice switching control unit at contacts 4P1-3-4P1-6 to which the nurse channel is already connected. The tone from the tone source is thereby transmitted to the patient. The above described operation of relay 5S completed an operating circuit for relay 5X through contacts 6S-4. Ground is thereby applied through contacts 5X-2 to the base of transistor 5T1 and the capacitor 5C2 discharges to subsequently turn the transistor off. Relay 5WT releases so removing the tone source from both channels. The RC time constant of this circuit determines the time for which the tone is applied. The above described operation of relay 4P1 releases relay 4NC by removing the locking circuit at break contacts 4P1-1, and so all previous visual and audible signals are removed and relay 4P1 initiates further ones. Continuous AC is supplied to the lamps SL1 and PL1 over contacts 4P1-2 and 4E-2 to leads 311 and 411. Ground potential is now removed from the base of transistor 4T2 allowing it to come on and apply ground potential through contacts 4E-6 to cause transistor 4T4 to conduct continuously and light the door lamp continuously. All these three visual signals are directed through break contacts of the 4E relay, which is only operated in an emergency and allows emergency signals to take precedence over others, as will be described later. The momentary presence of ground upon lead 401 from SSK1 and the negative potential from lead 504 through contacts 5N2-4 brings on transistor 4T1 to complete an operating circuit for relay 4P2 which is locked on via its own contacts 4P2-1 and 4P2-2. The locking path for relay 4P1 whose contacts 4P2-3. . .6 make the direct call connection is thereby transferred to a path through contact 4P2-6 and the switchhook contact of the patient handset. The operation of relay 4P2 disconnects the patient exchange wires 306, 307 from the exchange wires 304, 305 at contacts 4P2-4, 4P2-5 and connects them to the nurse communication channel wires 206, 207. The patient and nurse can now communicate and the circuit is ready for a possible transfer of the connection from the loudspeaker/microphone to the handset. Transfer of connection. To transfer the connection to the handset the handset is lifted thereby breaking the locking circuit for the relay 4P1 at the now open switch-hook contacts. The make contacts 4P1-3 . . . 6 therefore open and disconnect the communication channel PIC 1 from the nurse channel NIC. The handset is now connected to the nurse channel by the previously made contacts 4P2-5, 4P2-4. Replacing the handset completes the operating circuit for relay 4P1 and the loud-speaker and microphone are once again connected. Nurse to patient call. The nurse merely selects the patient station by using the SSK keys and the circuit operations are similar to those when the nurse answers a call. The patient will hear the short burst of tone to announce that the nurse is calling. If the patient was using the handset when the nurse calls then relay 4P2 would not operate although they can still communicate over the PIC1 channel. Disconnection. This achieved in three ways. The nurse handset may be replaced so removing earth from line 203 and causing the release of relays 5N1 and 5N2. The opening of contact 5N2-4 releases 4P1 and 4P2 to extinguish all the lamps and to break the communication links. If the intercom pick-up key IPK1 is released ground is again removed from lead 203. If the nurse selects another station by momentarily depressing another station selection key then all the P1 relays are released except the one wanted, as previously described. Remote station. Remote station key RTK1 is operated to connect the exchange lines 228, 229 and the buzzer lead to the remote station. If a patient calls the remote station buzzer sounds and lifting the handset applies ground to lead 218 bringing on relay 5SC. The closing of contact 5SC-1 brings on relays 5N1, 5N2. Since there is no provision at the remote station for selecting a patient station, the patients, if more than one is calling, are answered in turn by a preference lock-out arrangement. The make and break contacts -NC-6 of each patient station are arranged along the lead 402 as shown for contacts 4NC-6. If a patient is calling then the - NC relay has been operated and the make contacts closed and the break contacts open. The operation of relay 5SC has applied ground to lead 501, and since make contacts 4NC-6 are closed ground appears on lead 401 to operate relay 4P1 and produce similar circuit operations as when station key SSK1 was depressed. Since break contact 4NC-6 is open ground potential is not as yet directed to further stations. The locking circuit for relay 4P1 is transferred to the patient station switch-hook contacts when the relay 5X releases to disconnect the tone source. The remote station is connected to the nurse communication channel by leads 227, 226, the connection being broken at the end of a conversation by depressing the remote stat