. Betrieb und Einstellungen des automatischen Dreidrahttelefons. Eine Party auf einer Leitung kann geläutet werden und doch den anderen Abonnenten nicht die gleiche Leitung stören. Die Rin^ors, die auf dem Dreidrahtsystem verwendet werden, sind die harmonischen Klingeltöne. Diese Klingeltöne sind so eingestellt und konstruiert, dass sie auf verschiedenen Wechselzeiten von Lngcurrent klingeln. Die verschiedenen Frequenzzuständen werden bei der Austauschung durch eine speziell konstruierte Ringmaschine erzeugt.^ Im diskutierten System werden vier Stationen auf einer Parteileitung unterhalten, und^ist daher notwendig, vier verschiedene Frequenzen zu haben.die Bunduenzen waren die 16
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. Operation and adjustments of the automatic three wire telephone . one partyon a line may be rung and yet not disturb the other subscriberson the same line. The rin^ors used on the three wire systemare the harmonic ringers. These ringers are adjusted andconstructed to ring on different freciuencies of alternatLngcurrent. The different freq^uencies are created at the exchangeby a specially constructed ringing machine. In the systemunder discussion, four stations are maintained on a party line, and it is therefore necessary to have four different frequencies.The fret^uencies selected were the 16, SS, 50 and 56 cycles persecond. In common practice 66 cycles is about the highestfrequency that can be used for successfully ringing a bell soprogressive numbers were to give four frequencies and have themremoved as far as possible from each other. A general discussian j -44- —f-, —1 1 l_t , —nq.% 4 u |—^ r 1 , 1 —J ^£ ^ iiiiiii[iiiVJ1^1m innD 6 Fig. 10-Harmonic Ringer Assembly. 3.-, ^^y/7<2/r 7.- 7T//T^<^r ?T^<^^ rro/^ /7ufQ. ^/ect Ca. Trint. -silts ~is»^rvT^ ^ -4&- and description of one ringer will be given, and following thatthe essential differences between the different station ringersthemselves. Reference will be made to Figure 10 in the discussion A. Construction. The ringer coils are screwed to the ringer frame parallelto each other, ^ith a distance of about inch separating them. The iron core of each coil, which project about 5/5 inch, areslotted. The core frame, which supports the armature and clapperstem, is fitted permanently into these.slots. To the clapperstem, is fitted the vibrating parts. The most important of theseis the ringer reed which attaches to the core frame and the stem.The reed is a small thin piece of metal having a thickness of.058 inch. Its function is to allow the stem to vibrate freelyand having enough tension, to return stem to normal positinn.The reed is screwed to core frame at each end and is fitted overand up to the st
