. A study of wireless telegraphy and wireless telephony . Fig. 23 n Hughes Microphonicdree/- Carbon Defector. modifications have bet-n made to the microphonic detector justdescribed, Fig. 24 showing a granule of carbon between metallic-plugs in a tube. The microrhone de-tector is more sensitive than thefilings coherer, but it is more trouble-some . Fig. 24Carbon Gra_nu/e Defecfor . another form of crystal detectors is that used by Pickard,in which for his contact points he used several crystalline sub-stances, such as silicon, molybdenite, zincite, etc. This de-tector is shown in Fig. 25, and
. A study of wireless telegraphy and wireless telephony . Fig. 23 n Hughes Microphonicdree/- Carbon Defector. modifications have bet-n made to the microphonic detector justdescribed, Fig. 24 showing a granule of carbon between metallic-plugs in a tube. The microrhone de-tector is more sensitive than thefilings coherer, but it is more trouble-some . Fig. 24Carbon Gra_nu/e Defecfor . another form of crystal detectors is that used by Pickard,in which for his contact points he used several crystalline sub-stances, such as silicon, molybdenite, zincite, etc. This de-tector is shown in Fig. 25, and it works as follows: A metallicvessel V contains a layer of solder of low melting point, whichin turn is filled with some polished silicon. The brass rod Ris pressed down by the spring S until it makes contact with thesilicon ^ . Connections of the two separate rarts are made thru1) Gr. «(. Pickard, El. World, Vol. 48, p. 1003, U WPjckards Si/icon Defector. 29 L and K. Several experiments were madelately on crystal rectifiers by G. and following conclusionsarrived at: 1. The same phenomenon existsin the case of all contact detectorsusing crystal substances, such ascarborundum, anatase, silicon, iron pyrite, etc. 2. At the contact between the crystal and a common metal,or between two different crystals, or between two apparentlysimilar crystals, there is asymetric conductivity, permitting amuch greater current to flow in one direction than in the otherunder the same arplied voltage. 3. These contacts all have a rising current-voltagecharacteristic curve. 4. These crystals all have a large thermo-electromotiveforce against the common metals, and the amount and directionof this thermo-electromotive force is different at differentpoints on the crystalline bodies. 5. The rectifying effect is also different in amount anddirection at different points of the crystalline body. 6. Thermoelectricity doe
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