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Fig. 20 DC characteristics (speech condition) ERICOFON 700 - - - - DIALOG with carbon microphone and dial Fig. 21 (right) DC characteristics (impulsing condition) ERICOFON 700 - - - - DIALOG with carbon microphone and dial Fig. 22 Reference equivalents rel. NOSFER without transmission regulation SRE Sending WIRE Receiving SiRE Sidetone Fig. 23 (right) Reference equivalents rel. NOSFER with automatic transmission regulation tion, and the varying speech volume used by the subscribers, a distortionfree output power of about + 2 dBm is required for sending, which corresponds to an output voltage of about 3 V. This requires an amplifier operating voltage of about 6 V. As polarity protection is also required, the lowest d.c. voltage drop across the set becomes about 7.5 V, which corresponds to a telephone set resistance of 350—400 ohms at 20 mA. The direct current of the set, as a function of the feeding resistance (line resistance and current feeding resistance) in the speech condition is given in fig. 20, and in the decadic impulsing condition in fig. 21. For comparison purposes the corresponding curves for a conventional carbon microphone set (DIA LOG) are also given. It can be seen that the nominal difference in direct current between the two types is very small despite the fact that the nominal voltage drop across the electronic set is higher. Transmission characteristics As has been mentioned previously, ERICOFON 700 is constructed with an electronic speech circuit and electret microphone. Compared with the conventional telephone sets with carbon microphone ERICOFON 700 shows a number of improvements, such as — constant sending sensitivity — improved sidetone level — improved impedance of the set — sending distortion completely eliminated — current feeding losses eliminated If the transmission characteristics are expressed in reference equivalents rel. NOSFER it can be seen that the sending and receiving characteristics of an electronic set have the necessary prerequisites for achieving optimum or specified values.
Fig. 24 The impedance ot the telephone set and the local line Fig. 25 (right) Frequency curve for sending Fig. 26 Frequency curve for receiving Fig. 27 (right) Mean opinion score (MOS) as a function of the system reference equivalent (SyRE) ERICOFON 700: y = 3.43—0.00133 (x—S) 2 DIALOG: y = 3.31—0.00175 (x—2.14)' For the version without special transmission regulation the values shown in fig. 22 are those for the reference equivalents of the set for sending (SRE), receiving (MRE) and sidetone (SiRE). With a 0 ohm line SRE is + 3 dB, MRE — 4 and SiRE > 10 dB. For the version with transmission regulation during sending and receiving the values shown in fig. 23 are those for sending, receiving and sidetone as a function of the line resistance, including attenuation, with a 0.4 mm subscriber line. As can be seen from the figure, in the case with transmission regulation the efficiency of the telephone set is not dependent on type and length of the local line. The speech transmission circuit is designed so that the impedance exhibited by ERICOFON 700 is, in the main, identical to the impedance of the balance circuit. Since the balance circuit can match the impedance of the local cable very closely, the balance impedance has been dimensioned to match the line lengths to which the majority of the subscribers are connected, namely up to about 2 km. This means that as regards phase angle and absolute value the impedance of the set is of the same type and has the same value as the impedance of the local cable. Seen from the local exchange the impedance variations for varying line length, including the 0 ohm line, are thus very much smaller than in the case of conventional sets, fig. 24. The frequency curve of the set during sending is shown in fig. 25 and during receiving in fig. 26. The receiving curve is straight and independent of frequency, whereas the sending curve rises with frequency in order to compensate for the attenuation distortion on the local line. As regards sound reproduction the transmission quality of ERICOFON 700 is considerably better than the quality that can be achieved with a carbon microphone. It is well known that for high quality sound reproduction it is necessary to
Page 1: ERICSSON REVIEW 3 1976 GEOSTATIONAR
Page 4 and 5: Geostationary Telecommunications Sa
Page 6 and 7: 112 forever silent. The next launch
Page 8 and 9: 114 Figs. 1—4 Figs. 5—8
Page 10 and 11: 116 Figs. 17—20 Figs. 21—24
Page 12 and 13: Electronic Push-button Telephone Se
Page 14 and 15: The bottom part (frame) ot the set
Page 16 and 17: Fig. 10 Buzzer unit Fig. 9 Tone rin
Page 18 and 19: Fig. 12 Impulsing unit and ring uni
Page 20 and 21: 126 Fig. 15 Transmission diagram Fi
Page 22 and 23: 128 ed by about 100 kohms. In order
Page 26 and 27: 132 use a microphone in which the o
Page 28 and 29: CCM - A Well- tried and Economic Ma
Page 30 and 31: 136 ] Do not allow more staff in th
Page 32 and 33: Ten Years Experience of CCM in the
Page 34 and 35: 140 Table 2 Existing staff requirem
Page 36 and 37: Optimization of Power Supply Equipm
Page 38 and 39: 144 Initial expenditure. This consi
Page 40 and 41: Table 1 Acquisition costs for diffe
Page 42 and 43: 148 Fig. 8 Instead of feeding the p
Page 44 and 45: 150 Fig. 10 Apart from a highly sta
Page 46 and 47: Development, Production and Mainten
Page 48 and 49: 154 combined to meet the needs of e
Page 50 and 51: 156 duction and putting the package
Page 52 and 53: 158 Fig. 5 Working procedure when p
Page 54 and 55: 160 The error message is sent from
Page 56 and 57: Dr. Christian Jacobceus chaired the
Page 58 and 59: 164 Among the reasons that were giv
Page 60: TELEFONAKTIEBOLAGET LM ERICSSON PRI

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