Patent GB-654016-A (GB)
Title: Improvements in or relating to automatic supervisory arrangements in telecommunication systems and apparatus therefor
IPC: H04B7/155
Filed: 1948-10-11
Abstract: 654,016. Radio signalling. GENERAL ELECTRIC CO., Ltd., and ASPIN, J. J. E. Oct. 11, 1948, No. 26465. [Class 40 (v)] A telecommunication system including one or more unattended relay stations is provided with automatic supervisory arrangements which indicate a failure in the apparatus and provide a changeover to standby equipment. The arrangement may be applied to line communication but is described as applied to a frequency modulated radio link. The terminal transmitting apparatus, Fig. 2 (not shown), comprises a transmitter to which the normal modulation and a tone N1 is applied, and a standby transmitter. A monitor-detector coupled to the aerial is arranged to operate a relay TA on receipt of the R.F. oscillations modulated with the tone N1, the normally closed contacts of the relay TA being connected in the coil circuit of a slow-to-operate relay TB, which operates when relay TA is not operated, to change over to the standby transmitter, and operate an alarm. At the relay station, Fig. 3, the aerial 23 may be connected through a switch 25 to a receiver 8 comprising R.F. stage, mixer, oscillator, and I.F. stage, or to a spare receiver 12, the output of the receiver being connected to a transmitter 9 comprising I.F. stage, mixer stage and R.F. stage, this transmitter or a spare transmitter 13 being connected to the aerial 24 by switch 26 synchronized with switch 25. A monitor detector 27 is connected through a discriminator 52 to the receiver output and operates a relay A on receipt of the tone N1, and a monitor detector 28 is connected to the aerial 24 and operates relays B or C on receipt of R.F. oscillations modulated with tones N1 or N2 respectively. With the receiver 8 and transmitter 9 functioning correctly, relay A operates, to disconnect through the operation of relay E the high tension supply from an oscillator 33 whose frequency is the same as the incoming R.F. oscillations, and to ensure that the tone N3 generated at 30, and the tone N1 derived at 32 from the incoming signals in the opposite link are disconnected from the input to the transmitter modulator 31, the relay B through the operation of relay F disconnecting the tone N2 generated at 29. If the incoming signal modulated with tone N1 ceases, the relays A and B cease to be operated, the high tension supply is connected to oscillator 33, and tone N2 is applied to the modulator 31, the output of the transmitter being modulated by a tone N2 which operates relay C, causing relay D to switch the output of oscillator 33 via a mixer 34 to the input of transmitter 9, and connect the tone N1 to the modulator 31. This gives an output from the transmitter modulated with tones N1 and N2 providing an indication at the terminal receiver of the fault. Failure of receiver 8 during reception of the carrier modulated with tone N1, causes relays A and B to cease to operate and connects the H.T. supply to oscillator 33 whose output is applied to receiver 8, but failure of relays A, B and C to operate causes the slow-to-operate relay H, which operates if relay C plus at least one of the relays A or B fail to operate, to bring into operation the standby receiver and transmitter and apply tone N3 to the modulator of the standby transmitter, giving an indication at the terminal receiver that the change-over has occurred. If the failure occurs in the transmitter the relay B ceases to operate, and the relay H operates as for a receiver failure. The terminal receiving apparatus, Fig. 4, comprises a receiver 4 having a R.F. stage, mixer, oscillator, I.F. stage, and discriminator, and a standby receiver 6 which may be brought into operation by switches 38, 39 operated by slowto-operate relay RD which also operates an alarm. A monitor detector 41 is connected to the output of the receiver and operates relays RA and RB on receiving tones N1 and Nx respectively and also operates alarm devices 42 and 43 on receiving tones N2 and N3 respectively. If the incoming signal modulated with tone N1 is not received relay RA ceases to operate, causing an alarm to operate and connecting the H.T. supply to an oscillator 40 modulated with a tone Nx, and correct functioning of the receiver 4 causes the relay RB to operate, and relay RC to disconnect the H.T. supply from the oscillator 40. If the receiver 4 is faulty relays RA and RC will not operate, causing relay RD to effect a change-over to the standby receiver and operate an alarm.