Patent GB-1126286-A (GB)
Title: Communication systems
IPC: H04M9/00
Filed: 1967-01-23
Abstract: 1,126,286. Wired T.V. distribution and intercommunication system. GORDON A. FRIESEN INTERNATIONAL Inc. 23 Jan., 1967 [24 Jan., 1966; 6 Jan., 1967], No. 3386/67. Headings H4K and H4R. A wired television distribution system in a hospital, where each patient has his own receiver, is used also as an intercommunication system between the patients and a master station with the loud-speaker of the television receiver being used as the microphone and receiver of the intercommunication system and the cable, over which the television signals are fed to the receiver, being used both for message exchange and for the supply of power to the receiver. The communication may take place over a carrier frequency channel particular to the receiver with which communication is desired or the selection may be accomplished using a characteristic pulse train. Fig. 2 shows a patient's unit which is fed with signals and power from the master station over a coaxial line 2. The television signals are fed over a highpass filter 30 to the normal R.F., mixer, I.F., detector, video, and audio stages to be reproduced by the C.R.T. 12 and loud-speaker 14. When the master station wishes to call the patient the carrier frequency characteristic of that patient, e.g. fcl, is transmitted to be passed by the low-pass filter 48 to I.F. and detector stages 42 to cause them to operate switches 60, 62 and 63 which interrupt television programme reproduction and allows audio, modulated on the characteristic carrier, to be reproduced by the loud-speaker 14. If no audio is modulated on the carrier then the loudspeaker 14 acts as a microphone and feeds audio from the patient to a mixer 67, where it modulates a second, transmit, frequency fc2 characteristic of the patient, to be fed back on to line 2 to be received at the master station. If the patient wishes to originate a call then he presses a switch 70 which causes the selector 64<SP>1</SP> to generate the frequency #c2, e.g. by division of the television receiver's local oscillator output, which is fed via the mixer 67 to the line 2 for transmission to the master station. On reception of the frequency fc2 at the master station the frequency #c1 is reverted, received by the I.F. stages and detector 42 and switches 60 and 63 are operated to connect the audio channel of the television receiver to allow speech signals picked up by the loud-speaker 14 to modulate the local carrier frequency fc2 to be transmitted to the master station. If privacy is desired a loud-speaker located in the lavatory or a handset located in a nursing alcove may be used in place of the loud-speaker on the television set. In this case the call control unit 69 makes the appropriate connections and switch 80 disconnects the T.V. receiver loudspeaker. The selector 64<SP>1</SP> is switched to allow two different carrier frequencies to be used, one for normal calls and one for emergency calls requiring priority attention. Monitoring equipment, e.g. of heart beats, may be connected at jack 90 to cause the emission of the emergency signal automatically in an emergency. Fig. 3 shows the master station equipment in which, when the master station wishes to call a patient, a switch 102 is rotated to a position to select that patient, as indicated at 101, which causes oscillator 115 to be tuned to that patient's characteristic frequency, e.g. by the selection of the appropriate tuning capacitor at 117. The frequency is applied via a mixer 116, where it may be modulated by the output of the handset 104, to a switch 201 which is closed when the handset is removed from its rest. The signal is thus applied to the line 2 for transmission to the patient's apparatus. Incoming signals are received by tuned amplifiers 119 and the output from the appropriate amplifier, selected by switch 121 coupled to patient selector switch 102, is passed to the handset receiver, 104. When a patient wishes to originate a call the signal emitted from the patient's apparatus is received at the appropriate one of amplifiers 119 which causes, via the visual display alarm unit 142, the appropriate one of the signal lamps of the banks of lamps 106, 108 and 109 to be illuminated; indicating that a patient is calling. The master station operator then turns switch 102 to the appropriate position to communicate with that patient. Should more than one patient wish to communicate at one time, then a memory unit 140 is actuated to store the calling signals in order of time of arrival or priority, so as to allow them to be answered, either manually or automatically, in appropriate order. The handset 104 may also be connected with a normal telephone system via switch 170 and a normal telephone dial 167 is provided for use at such times. Two similar systems may be arranged each covering half the patients on a single floor with the two master stations side by side so that, at busy times two operators man the equipment while at slack times one operator will control the two stations. A television camera may be arranged at the master station focused on the operator so that a picture signal may be transmitted to the patient to whom the operator is speaking. In this case the patient's apparatus may include a T.V. set with a channel selector which is automatically operated, when that patient's characteristic signal is transmitted, to tune the receiver to a channel over which pictures from the camera at the master station are being transmitted, Fig. 9 (not shown). In this system the audio signals from the master station may be transmitted with the video signals as in a normal television signal, Fig. 11 (not shown). Also described is a modification to allow private communication to take place between the nursing alcove and the main station without the patient's T.V. programme being interrupted, or the patient being able to overhear, Figs. 12 and 13 (not shown).