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20 utilizing the cable for even larger systems. Nowadays {he normal coaxial cable (2.6/9.5 mm) is justified only for 60 MHz systems. Small-core coaxial cable (1.2/4.4 mm) is very suitable for 12 MHz systems and even for 4 MHz systems when the traffic requirement is limited. On the other hand it is very doubtful whether it will be possible to justify 1.3 MHz systems in the future. Fig. 6 shows a comparison of the route construction costs for different coaxial cable systems. The calculations have been carried out for a line section of 100 km with normal and small core coaxial cable respectively. The cost of the cable and the laying costs have been included and also the cost of the repeater equipment and its installation. The distribution of the route construction costs per circuit kilometre is shown in fig. 7. The change to transistorized coaxial systems also resulted in a substantial reduction of the operational and maintenance costs. Power consumption fell by more than a power of ten, preventive maintenance was eliminated and repair costs were reduced. All in all the direct operational and maintenance costs for transistorized systems constitute only about 5 % of the corresponding costs for valve-type systems. The future of coaxial cable systems Coaxial systems and radio-relay links have been the dominating transmission media in the long-distance network for telephony for very many years. This development can be expected to continue for another ten years or so, before digital systems with high capacity have left the experimental stage and become commercially competitive. Naturally for certain applications satellites and sea cables are attractive alternatives, but quantitatively these are not so important. The choice between coaxial systems and radio-relay links is influenced by a number of factors. As a general rule radio-relay links have the advantages that the route construction costs are lower and the time needed to install them is less. On the other hand the coaxial cable alternative provides the possibility of successively increasing the number of circuits by converting to larger systems. The cables that were originally intended for 4 MHz systems (960 circuits) have proved to be satisfactory for 60 MHz systems (10,800 circuits). The long life of coaxial cables, the conversion possibilities, their reliability and the low maintenance costs makes for a very competitive annual cost per circuit. Even the traditional "radio-relay link countries" have begun to evince an increasing interest in coaxial systems during recent years. Contributory reasons for this are that — the traffic requirement on certain routes is so great that the capacity of radio-relay links is insufficient — the frequency bands that are allocated for radio-relay links are already exploited to such a high degree that the introduction of further radio-relay links is becoming increasingly difficult. This applies particularly in the vicinity of most of the large cities and towns in the world. The coaxial cables that are installed represent a very large capital investment, and there are very strong reasons for increasing their capacities even further. Investigations that have been undertaken recently indicate that the existing tube construction can be used for frequencies well above 60 MHz. Preliminary investigations of systems with bandwidths in the region of 150 to 200 MHz are going on in several countries. Another alternative, which appears to be promising, is to introduce digital coaxial systems with high capacity. This development line is favoured by a general tendency towards the digitalisation of telephony. A digital system with a capacity in the order of 1 Gbit/s (equivalent to roughly 15,000 telephone channels) can become a reality within 10 years. Compared with waveguides and optical fibres such a coaxial system should prove to be extremely competitive.
Automatic Transmission Measuring Equipment, ATME 2, for International Telephone Circuits Arnold Soderberg LM Ericsson started ten years ago to manufacture the automatic transmission measuring equipment described in Ericsson Review', 2 7963. It is made in two models, ATME 1 for international circuits and ATME N1 for national. As a result especially of the experience gained with ATME 1 and of new technical depelopments, CCITT have drawn up new recommendations for an automatic transmission measuring equipment for international circuits, ATME 2. LM Ericsson have been represented on the working group concerned within CCITT and have since developed ATME 2 in accordance with these recommendations 3 . ATME 2 has considerable advantages over ATME 1. UDC 621. 317. 799: 621.395. 126 LME 8076 1548 1001 Fig. 1 Transmission measuring equipment ATME 2 with directing and responding equipment Type a on the left-hand rack. On the right-hand rack exchange interlace equipment and responding equipment Types b and c. On the rack to the rear, individual test block for individual selection in ARM. Tape punch, tape reader and typewriter are used as input/output devices. The need for automatic measurement of transmission characteristics on international circuits becomes more acute with the rapid increase of international traffic. A number of administrations have already experienced through ATME 1 the considerable technical and economical advantages provided by such a measuring equipment. Compared with ATME 1, ATME 2 offers the following significant advantages among others: — the signalling system for communication between directing and responding equipments is less sensitive to disturbances. The signalling functions partly on the compelled sequence principle and the frequencies of system No. 5 are used. — the absolute noise value can be measured instead of merely setting a threshold which indicates accept/ reject. — the speed of attenuation and noise measurement is five times greater, so that three sets of circuit measurements can be made per minute. This reduces the circuit occupation time and the entire measurement program can be carried out more quickly. — TASI circuits and circuits containing echo suppressors can be measured. — ATME 2 can be called up by a maintenance centre from which it can be controlled and to which the results of measurements can be transmitted. — three stores for individual line data have been introduced which, among other things, increase the measurement capacity. The speed has been achieved through the use of electronic equipment. The
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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
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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: Fig. 7 Relative route construction
Page 31 and 32: Fig. 3 ATME 2, block schematic. Dir
Page 33 and 34: 600 ohms and the absolute value of
Page 35 and 36: uring signal received from the circ
Page 37 and 38: WORLDWIDE NEWS Worldwide expansion
Page 39 and 40: Joint telecommunications venture in
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