Patent GB-800308-A (GB)
Title: Apparatus for automatically determining at a distance the largest distortion of telegraph signals in a start-stop code transmitted by a subscriber's station
Inventor: SNIJDERS ANTONIE
IPC: H04L12/26
Filed: 1955-12-29
Abstract: 800,308. Telegraph systems. NEDERLANDEN STAAT DER, DIRECTOR GENERAL OF POSTAL & TELECOMMUNICATIONS. Dec. 29, 1955, No. 37327/55. Class 40 (3). A telegraph system includes measuring apparatus which is located at an exchange and which after selected by a subscriber in response to predetermined combinations of signals determines the maximum distortion occurring in the transmitted signals and transmits signals indicating the distortion to the calling subscriber. The operations at the exchange are generally controlled by a timing circuit producing pulses to examine the received signals, timing pulses to evaluate the distortion and further pulses controlling the transmission of the signals to the calling subscriber. In the diagrammatic arrangement of Fig. 1, the signals received,at the input circuit IN at an exchange operate a start-stop circuit SS controlling a generator G operating at a frequency of 1000 c.p.s. and controlling the time circuit TS incorporating a number of distributers providing series of pulses for different purposes. The incoming signals are passed along a second path to a signal-detecting circuit A1 fed with pulses from TS at 30, 50 ... msecs. from the beginning of the signal so that the signals in coded form are stored on memory circuits 01 ... 05 before being passed to detector circuits CL, MV, V allowed to become operative at the end of a code signal, the circuits MV and V being responsive to the signals, " Who are you ? " and " ? " respectively when preceded by the figures signal operating the circuit CL, and the circuit MV being operated conjointly with the operation of the circuit V. The operation of the circuit MV brings into operation a distributer 16VV controlled by the circuit TS and also a circuit BO comprising a number of rectifier networks to produce a sequence of sixteen 5-unit code signals including the designation of the measuring set and the name of the exchange, which are passed in succession to five transmitting relay circuits Z1 ... Z5 from which they are passed in succession to a transmitting circuit OZT. The output of this circuit passes via a circuit B1 controlled by the circuit CL, MV, V to a circuit U transmitting the signals to the line leading to the subscriber. The transmitted signals are also passed to the auxiliary circuit CU including the receiving magnet OVe of a teleprinter at the exchange. The signals recorded on the circuits O1 ... 05 can also be passed via the circuit OZT to the receiving device OVe of the circuit CU, but are not passed to the output circuit U since the circuit B1 is closed until the circuits CL and MV have been operated. The incoming signals are also passed to a circuit P producing at each transition from mark to space, or vice versa, a positive pulse fed to a set of distortion-measuring circuits D5, D10 ... D25 producing, in combination with pulses from the timing circuit TS registration of percentage distortions 5-10, 10-15, 15-20, 20-25 and greater than 25 respectively. The transmission of the distortion figure is requested by the transmission of figures followed by the signal for ? with the operation of the circuits V and MV, the former controlling the circuits D5 ... D25 to effect the modifications of the signals set up in the circuit BO to represent the limits of the maximum detected distortion, the setting up and passage of the signals to the circuits Z1 ... Z5 and to the transmitting circuit OZT being controlled by TS and 16VV which are set into operation as the result of the operation of MV in conjunction with V. The primary distributer holds the circuit TS in operation irrespective of any signals at the input IN until the circuit MV is released. The accuracy of the timing circuit TS is checked by circuits SC, SI and SF, the circuit SC being operated by a switch so that a circuit SI is triggered by pulses at 50 cycles from a circuit SF to pass pulses to a set of neon lamps to which pulses are applied from appropriate terminals of the timing circuit TS so that the lamps are illuminated in the same succession if the operation of TS is correct. A transmitter ZVe may be used by the exchange operator to communicate with the calling subscriber. Specifications 498,373, [Group XL], 765,953, 765,954, 780,003, [both in Group XL (c)], and 799,930, [Group XIX], are referred to.