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26 Fig. 4 Principle of measuring device S Sending unit MO Object to be measured F Measuring amplifier R Relay for switching between noise and attenuation measurement D1 Detector for attenuation measurement D2 Detector for noise measurement J Comparison circuit DL Pads UREF Reference voltage source RK Counting chain OSC Clock oscillator UTL Read-out circuit ST Control unit nal has been received by the directing equipment the circuit is cleared. If there is no assistance operator signal, code 11 in ATME 2's signalling scheme is sent instead. Responding equipment Type b is designed as an independent code answering equipment and performs the same function in respect of signal system test as described for Type a. Responding equipment Type c is used for supervision of the busy flash signal and is a busy-marked code answering equipment. It sends a busy flash signal when called. This equipment, however, can often be replaced by strapping in the regular exchange registers. The strapping results in busy on a call to the number reserved for the purpose. Salient feature of the measuring device Measurement of one speech channel of a four-wire circuit is done in the directing equipment. Thereafter the other speech channel is measured in the responding equipment and the result is transferred to the directing equipment with ATME 2's own signalling system. In the following survey the measurements only in one direction will be dealt with, since they are performed in the same way in the other direction (fig. 4). Send unit The three measurement frequencies 400, 800 and 2,800 Hz are generated by a corresponding number of oscillators with level supervisors and alarm circuits. For the special locking tone required for tests of TASI circuits, 2,800 Hz is also used. Disconnection of echo suppressors is done with 2,100 Hz tone generated by a separate oscillator. Instead of an oscillator for 800 Hz, a 1,000 Hz oscillator can be supplied on request. Attenuation measurement The measurement tone sent from the send unit is received at the other end of the circuit by the receive unit. There it passes through amplifier F, contact R and signal detector D1, where it is rectified and fed to one input of the comparison unit J (fig. 4). To the other input of this unit is fed a reference DC voltage generated by the reference voltage source UREF. The reference voltage passes through the pads DL, in which it can be lowered by altogether 35 dB in steps of 0.1 dB. The pads are connected into circuit by field effect transistors which permit an extremely rapid measuring process. The successive connection of the pads is controlled indirectly by the clock oscillator OSC. The latter is started by a pulse from the control unit ST when the measuring sequence is to stop and feeds a counter chain RK, which in turn steps the pads DL in steps of 0.1 dB. In the comparison unit J a comparison is made between the level of the meas-
uring signal received from the circuit and the reference DC voltage. When, after passing through the pads, this voltage has fallen to the same level as that of the measuring signal, the comparison circuit J sends a stop signal to the clock oscillator and stepping of DL ceases. The time during which stepping of DL has taken place is proportional to the attenuation connected. The stepping time is translated into an attenuation value which via UTL is fed to the control unit. Noise measurement The control unit connects a 600-ohm termination at one end of the speech channel. At the other end the measurement is carried out. The circuit noise passes through amplifier F and relay contact R1, after which it is fed to detector D2, which consists of a psophometric filter, a square-wave rectifier and an integrator. In the comparison unit J the integrated DC voltage is compared with the reference voltage from the cascade-connected pads DL on the same principle as for attenuation measurement. Supervision Before each measurement the measuring device automatically supervises the programmable pads. In the event of a fault the equipment is blocked and an alarm is issued. The outgoing send level is also supervised automatically. The measuring device can also be supervised by measurement of supervisory pads connected into circuit by the control equipment. The result is printed out and an automatic indication is obtained as to whether the values are within the permissible limits. By means of a special supervisory unit, equipment can also be calibrated manually. Input and output Input of circuit data and output of the results of measurements are done with the I/O devices in the following manner. Circuit and route data From a typewriter the following common data can be fed in as required: 27 — numbers of the routes to be measured — measuring routine, which together with the individual class number of the circuit decides which measurements are to be carried out — printout of all results of measurements or only of those outside the tolerance limits — control of measuring time common to all routes through indication of start and possibly also stop time. The following individual circuit and route data are fed in from the tape reader: — control of measuring time per route through indication of start and stop time — identity number of circuit — circuit access number — individual class number of circuit — call number of responding equipment — nominal loss of circuit and permissible deviation — measuring signal level either 0 dBmO or — 10 dBmO. Printout of results With the arithmetical unit ARU a check is made that measured values are within the tolerance limits. There are two such limits. One marks that the circuit must be repaired and the other that it must be removed from service. The results of measurements can be printed out on the typewriter and in parallel on a tape punch, or solely on a tape punch. It is possible to print out on the typewriter only those values which are without the tolerance limits and, on the tape punch, all measurement results. The latter can then be analysed statistically in a computer. Some examples follow of the information — apart from the exact values of
Page 1: ERICSSON REVIEW 1 1974 ELECTRONIC T
Page 5 and 6: ERICSSON REVIEW NUMBER 1 1974 • V
Page 7 and 8: Fig. 1 LC oscillator, circuit diagr
Page 9 and 10: Fig. 4 RC oscillator, circuit diagr
Page 11 and 12: Fig. 7 Decadic electronic pushbutto
Page 13 and 14: Fig. 11 Electronic speech circuit,
Page 15 and 16: Fig. 15 (left) Frequency response,
Page 17 and 18: Coaxial Cable Systems: Operational
Page 19 and 20: Fig. 2 Pilot regulation. 12435 kHz
Page 21 and 22: Fiftieth Anniversary of Ericsson Re
Page 23 and 24: Fire-Alarm Installation in the Sama
Page 25 and 26: Fig. 5 Noise as a function of the l
Page 27 and 28: Fig. 7 Relative route construction
Page 29 and 30: Automatic Transmission Measuring Eq
Page 31 and 32: Fig. 3 ATME 2, block schematic. Dir
Page 33: 600 ohms and the absolute value of
Page 37 and 38: WORLDWIDE NEWS Worldwide expansion
Page 39 and 40: Joint telecommunications venture in
Page 41 and 42: The Ericsson Group With associated

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