88 THE BELL SYSTEM TECHNICAL JOURNAL, JANUARY 1957 



small "non-inductive" winding for resistance. The inductor on the bot- 

 tom in Fig. 14 illustrates one type in which the non-inductive part of 

 the winding is placed on one of the separating fins. In some cases, capaci- 

 tors and resistors were also combined. Fig. 15 shows two of these. The 

 capacitor at the bottom right contains three capacitances and a single re- 

 sistance in the same container. This construction requires that the re- 

 sistor parts be capable of withstanding the capacitor drying and impreg- 

 nation process and also that the resistor contain nothing which would 

 be harmful to the capacitor. The capacitor on the left in this figure is 

 housed in a ceramic container on which is wound a resistor. The capaci- 

 tor at the top is a high-voltage type Avhich, aside from electron tubes, 

 represents the largest single component used in the repeater. In this ca- 

 pacitor, the tape terminals which contact the electrodes are brought out 

 through the ceramic cover and are made long enough to reach an ap- 

 propriate point so as to avoid additional soldered connections. Such 

 special designs introduced many problems in the manufacture of the 

 components. However, the improved performance of the repeater and 

 the increase in the inherent reliability of the overall system fully justified 

 the greater effort which was required for the production of such special- 

 ized apparatus. 



POWDER BY-PASS GAS TUBE* 



The fault locating means, referred to previously, requires that the 

 power circuit through the cable be continuous. To protect against an 

 open circuit in the repeater, such as a heater failure, an additional de- 

 vice is required to bypass the line current. This bypass must be a high 

 resistance under normal operating conditions since anj' current taken 

 b}^ this device must be supplied through preceding repeaters. If an open 

 circuit occurs the bypass must carry the full cable current. At full cur- 

 rent, the voltage drop should be small to avoid excessive localized power 

 dissipation in the repeater. The de^'ice should recover when power is 

 removed so that false operation by a transient condition will not perma- 

 nently bypass the repeater. 



A gas diode using an ionically heated cathode has been used to meet 

 these requirements. By making the breakdown voltage safely greater 

 than the drop across the heater string, no power is taken by the tube 

 under normal repeater operation. In the event of an open circuit in the 

 repeater, the voltage across the tube rises and breakdown occurs. Full 

 cable current is then passed through the gas discharge. Removal of power 



Material contributed by Mr. M. A. Townsend. 



