Patent GB-772733-A (GB)
Title: Improvements in or relating to the supervision of unattended repeater stations
Inventor: DODD GEORGE ALEXANDER
IPC: H04B17/40
Filed: 1954-03-02
Abstract: 772,733. Repeating systems. BRITISH TELECOMMUNICATION RESEARCH, Ltd. Feb. 11, 1955 [March 2, 1954], No. 6156/54. Class 40 (4). In a communication system having unattended repeater stations each station is allocated a pair of characteristic signalling frequencies each of which may be transmitted continuously, interrupted at 10 c.p.s., or suppressed to indicate the normal condition and various fault conditions, the fault signals having a definite order of priority so that a signal for a fault of high priority takes precedence over signals for faults of low priority. The same signalling channel which may be a phantom circuit is used for faults in a number of unattended stations. At each unattended station the output of oscillators O1 (X tone), and 02 (Y tone), Fig. 2, is fed on to the signalling channel through equipment SE which chooses the signal according to the condition existing at the station. Signals from preceding stations pass through an equalizer E2 and the combined signals pass on to the next station through hybrid transformers HT3, HT4, and dual amplifiers A3, A4. On reaching an attended station the signal is equalized and amplified and then split into its component characteristic frequencies by band-pass filters. The two frequencies characteristic of an unattended station then pass to separate receivers the outputs from which operate an alarm and indicator panel. Power for the control equipment at an unattended station is supplied over a line a or b, Fig. 3, depending on whether the power is normally supplied or is supplied in an emergency. The normal signal is obtained with continuous X and Y tones applied to the signal channel via terminals T1, T2, when contacts ab1, ab2 of relay AB are made. Relay AB falls back only if the power supply fails in which event both tones are removed from the channel and no other fault signal can be sent from that station. A test key KA can break the circuit of AB and test keys KB to KH can bridge the terminal pairs 2 to 8, each pair being bridged by the occurrence of a particular fault. Either the X tone or the Y tone or both can be interrupted by contacts of a relay IG which is arranged to interrupt its own circuit at 10 c.p.s. when either the X or Z relay pulls up. The fault signal second in priority to power failure is given for burglar or fire alarm and bridges the terminals 2 to operate relay V which pulls up relays W and Z and results in the transmission of an interrupted Y tone under the control of the interrupting relay IG. A cable fault in the next repeater section gives the third priority and bridges terminals 3 to actuate relay U, provided relay V is not actuated. This operates relays X and Y and results in the transmission of an interrupted X tone. A power unit fault gives fourth priority by bridging terminals 4 and actuating relays X. and Z to send both tones interrupted. Fifth priority if given to fuse and valve alarms which bridge terminals 5 to actuate relay W alone, contacts of which cut out the X tone and apply continuous Y tone to the line. Sixth priority, due to voltage variation, bridges terminals 6 and actuates relay Y alone, contacts of which disconnect Y tone and apply continuous X tone to the line. Changeover of power supplies from normal to emergency, bridges terminals 7 and gives a seventh order of priority with relay X operated alone to send interrupted X tone while continuous Y tone is also applied. Last priority is given to pilot deviation alarms which bridge terminals 8 to actuate relay Z alone so that X tone continuous is transmitted with Y tone interrupted. At an attended station the receivers corresponding to the X and Y tone of the unattended station under consideration control relays RAX and RAY respectively, Fig. 4, the contacts of which pull up when a continuous tone is received and follow the interruptions of an interrupted tone. Relay RAX controls relays XA, XB, and XC, the contacts of which, together with those of relays YA, YB, YC controlled by relay RAY, light one of the pilot lamps LP1 to LP9. Lamp LP1 indicates power, failure, LP9 indicates normal working, while lamps LP2 to LP8 indicate faults corresponding to like numbered terminals at the unattended station. Normally, continuous X and Y tones are received so that contacts rax, ray are pulled up. A master key MK controlling relays RR, one of which is associated with each pair of relays RAX, RAY, sets the receiving equipment by completing the circuits to relays XA, XB and YA, YB, each of which have self-holding contacts. Alternatively use may be made of a key KR individual to the relays RAX, RAY. With the application of continuous X and Y tones relays XA, XB, YA, YB will be actuated and relays XC and YC disabled once the relays have been set bypulse from either of the keys MK or KR. In this condition lamp LP9 lights and a relay BA opens a: bay alarm circuit on terminals T13, T14. Alarm circuits connected to terminals T11, T12 and to T15, T16 are also open. If, say, the X tone is interrupted while the Y tone remains continuous, indicating a fault of seventh priority, relay XA falls back on the first interruption and actuates XC while relay XB, which is slugged, remains operated. In consequence, lamp LP7 lights and a relay UA operates to disable the urgent alarm on terminals T11, T12 and operate the non-urgent alarm on T15, T16. If, for example, a fault of third priority is received X tone continues interrupted while the Y tone is suppressed, lamp LP3 lights and the urgent alarm on T11, T12 is actuated. ' In the event of a cessation of the X or Y tones relays XA and YA will remain disabled until reset by one of the keys MK or KR which can consequently cancel the effect of a signal which has been discontinued and superseded by another signal. Specification 744,340 is referred to.