Patent GB-1207450-A (GB)
Title: Communication system
IPC: G08B3/10
Filed: 1968-03-21
Abstract: 1,207,450. Interconnection systems. INTERNATIONAL STANDARD ELECTRIC CORP. 21 March, 1968 [22 March, 1967], No. 13706/68. Heading H4K. In a communication system wherein a calling party is connectible to any one out of a plurality of free stations in a group, the order of preference for seizing a free station is determined by the identity of the calling party. The system is applicable to a hospital where nurses may be present in any one or more rooms on a floor and it is preferable that the nurse nearest to a calling patient be called. Each floor has its own "exchange" (see below) and these are interconnected so that if a nurse does not respond to a call on the caller's floor then a hunt for a nurse on an adjacent floor is made automatically. Each exchange can handle only one call at a time. Particular description.-The five out stations (station 2 is shown in Fig. 1) are identical to each other and their terminals E2-L2 and M2, N 2  are multipled together and to corresponding terminals at the non-communicating main station or exchange (Fig. 1). The terminals X and Y are however individual to the stations and are connected to tags on what may be considered as a call-finder SMZ and a PBX final selector SMV1, SMV2. A nurse indicates her presence in a room by operating locking key PK and thus bringing up relay Prr whereby room indicator lamp KL and door lamp VL are energized and an earth marking is applied to the terminal X3 (not shown, but equivalent to X2). If a patient in room 2 calls by lifting his handset THS and operating non-locking key AK, relay Ar comes up to apply calling battery to terminal X2 and to energize room lamp KL. Relay Gor in the exchange follows whereby a floor lamp GL is energized, a door lamp PL is flashed at a 660 msec. rate by multivibrator SMV and finder SMZ is started. When the latter encounters battery on tag 2 of level LA, Tzr comes up, to stop the stepping, to bring up Phr in station 2 and supply battery to the caller's handset, and to mark lead z2 which extends to the selectors SMV1/SMV2. The latter both step round (magnets energized via go2 and tz2) until stopped by the operation of relays Tpr1/Tpr2 when the marked lead z2 is found. Relay Tptr follows so as to restart the selectors in their quest for the nearest nurse station. Since in this case a nurse is present in room 3, 8MV1 stops first by the operation of relay Tvr1 to marking earth on tag 3 of level LA and SMV2 stops when it reaches tag 00 (due to off-normal contact SM U2). If there had been nurses in rooms 1 and 2 the relays Tvr1/ Tvr2 would have raced and the victor then stopped its own selector and caused the other one to step-on to tag 00. Battery is reverted over tag 3 of level LB to the nurses station wherein relay Phr comes up to connect calling tone from TO to the loud-speaker LS (this also occurs in the caller's room since the equivalent relay Phr is up 1. When the nurse replies by lifting her handset THS, relay Str in the exchange comes up to cut-off the tone from the loud-speakers in both rooms and microphone current is supplied over level LB of selector SMV1. If no action is required the nurse operates key UK before hanging up whereby all the circuits are returned to normal (apart from SMV1 which remains on tag 3). If the nurse has to see the patient however she hangsup (then releases her presence key PK) whereby Cr in the caller's room comes up and lamp PL lights continuously. When the nurse enters room 2 and operates key PK she may then make an alarm call by actuating AK whereby Egr comes up to connect relay Tnr and floor lamp GL to multivibrator SMV whereby regularly interrupted tone and lamp signals are given (normal tones are governed by multivibrator AMV which has a 2 sec. on 28 sec. off cycle). If a nurse enters room 2 and operates PK before the (original) call is answered, the calling condition is removed and all circuits restore. A patient may initiate an urgent call by operating PSK whereby relays Zzr and Tnr interact to provide an asymmetric tone pattern. If a nurse cannot be found i.e. if selectors SMVr1/SMVr2 have stepped round to their 00 tags, relays Tfrl/Tfr2 come up to slowly release Tptr. The latter releases Tfr1/Tfr2 so that SMVr1/SMVr2 can step round again in the search for a nurse. Eventually if no nurse is found an alarm AB is energized by time-out circuit TC. As mentioned above, nurses on adjacent floors may be called if the home exchange fails to find a home nurse after two cycles of selectors SMVr1/SMVr2 (Fig. 3, not shown).