Patent GB-722877-A (GB)
Title: Improvements in audible and visual two-way communication and annunciation system forhospitals and the like
IPC: G08B5/22
Filed: 1953-02-03
Abstract: 722,877. Intercommunication systems. COMMERCIAL RADIO-SOUND CORPORATION. Feb. 3, 1953 [Feb. 12, 1952], No. 3048/53. Class 40 (4). [Also in Group XXXVIII] In a telephone intercommunication system having a central station and a number of substations each with a single manually operable switch a selector switch is stepped in response to the operation of one of the manual switches to find the substation placing the first call and display its identification at the central station and, on conclusion of the conversation between the central station attendant and the caller, to seek for further calls which may have been subsequently initiated before returning to its normal or home position. The system described is a hospital network wherein the central station is the floor nurse's room and the substations are patients' bedside loud-speaker/microphone sets. Directional switching of a one-way amplifier is controlled manually from the central station or by a voice-operated switch. Provision is made for transmitting tone signals successively to all the substations and for supervision of all the floor central stations by a head nurse who can herself answer any unanswered calls on any floor. The system also describes a recording arrangement for recording the total times of unanswered calls on each floor central station and an arrangement for indicating to the head nurse that a call has been waiting for more than a predetermined period of time. Operation of push-button 100c in the semi-private room BC, Fig. 5A, energizes calling relay 103c which lights the dome lamp 114c outside the room and pilot lamp 104c. The relay 103c is self-locking and energizes relay 119 which in turn energizes a relay 192 to step a multi-bank selector switch 167 to the calling patient's position where the " A " contact is ungrounded, light call-awaiting dome lights 126 and 137-140 at various points on the floor, and energize a buzzer 146. A relay 208 in parallel with stepping relay 192 short-circuits the amplifier output during the stepping to suppress stepping clicks. The central station attendant in raising the handset 148 operates a relay 132 which releases relays 103c and 119, and puts out pilot light 104 and the call-awaiting dome lights. Light 126 on the control panel remains lighted if another station is calling. The call may be answered personally by the attendant, in which case the call is cancelled by a key 106 at the local station. On replacement of the handset 148 the selector seeks a further caller or returns to its normal position if there are no waiting calls. Relay 208 is then released. The central station may set up a call to a substation by means of switch 152 which actuates relay 132 and 188 to step continuously, through relays 208 and 192, the selector switch 167 until it is stopped by the attendant releasing switch 152 when the wanted position is reached. Alternatively, switch 167 may be stepped from contact to contact by throwing and releasing a switch 151. Calls made by patients during such stepping operate a locking relay 129, which operates relay 195 to prevent the release of calling relays 103 by a short-circuit through the " B " level contacts whether or not the handset 148 is on its rest. Patients' rooms can be remotely supervised by listening on loud-speaker 226 for abnormal sounds in each room in succession, but the patient's set includes a secrecy switch 173 to prevent listening in to conversation. Switch 259 energizes a relay 195 to complete the selector stepping circuit which includes relays 192 and 208 and cam-actuated contacts 233, 234. The loud-speaker is disconnected at each step to prevent objectionable clicking; and the switch can be stopped for prolonged observation of a particular room by lifting the handset 148. An incoming call interrupts scanning by actuating relay 119, which releases relay 195. In order that the wipers shall not wait on unused contacts, " A " bank contacts of out-of-use positions are directly grounded and the " E " bank contacts are commoned to one side of relay 129. Relay 195 is thus released on arrival of the selector wipers at an unused position and the wipers are then stepped rapidly to the next " in use " position. The " E " bank contacts may be connected to relay 129 by a metal plug in the panel indicating lamp sockets 524. Tone signalling to each patient in succession is effected by a key 214 energizing a relay 214a which operates a further self-locking relay 211 to remove an earth from a neon oscillator 268, step the selector switch in a similar manner to switch 152, and operate relay 132 to feed power to the amplifier and render it operative in the required direction. Tone which is adjustable as regards frequency and volume is fed over a screened lead 280 to the grid of valve 218 and the cathode circuit of valve 217 is broken by relay 211 to prevent interaction and feed-back. Key 214 may be held closed so that the transmission of tone may be repeated. A master remote station or head nurse's station, Fig. 7, can monitor visually all central panels on various floors and answer any waiting call on any panel by means of a floor selector switch 306. In order that waiting calls on floors shall not be cancelled by switch 306 as it passes through the contacts of each, a mechanically interlocked switch 305 is provided to open the circuit. The station also includes an integrating recorder, Fig. 6 (not shown), for recording the total time that calls are unanswered and a dome lamp 511 for each floor which indicates that a call on that floor has been unanswered for more than a predetermined time. The handset 308 is switched to be in parallel with a floor central station handset to answer calls. A five-gang multiple switch 400, Fig. 8 enables the head nurse to call any central station. A dual loud-speaker-microphone, Fig. 9 (not shown), is used and after the floor has been selected the circuit of a self-locking calling relay 421 is closed by a manually-operated switch 423. Relay 119 operates at the wanted central station and both audible and visual indications are given that the head nurse is calling. The calling relay 421 is released when handset 148 is lifted as in the case of patients calling. An arrangement whereby an important room such as an operating theatre can call any of the stations but cannot itself be called is described with reference to Fig. 10 (not shown), and a voice-operated switch wherein the directional relay 244 is included in the anode circuit of a normally cut-off valve, and the normally effective direction of transmission is towards the central station is also described.