Phototelegraphy. Baretters. Condensers. 



933 



62 080. 1 : 5. 



Si-leniuin Cell is illuininatod through a film constructed cylindrically and arranged to move after the manner 

 of the phonograph cylinder. The cell is connected up in common with supply at constant pressure, with 

 the travelling lead, and at the receiving station, with the movable system of a light relay. All fluctuations 

 caused by the successive and variable degrees of illumination of the Selenium Cell produce corresponding 

 variations in the moving system of the light relay. The latter is placed between a Nernst lamp and a 

 second photographic film, also cylindrical in form and arranged so as to be movable, this second film ro- 

 tating synchronously with the film at the transmitting station. An opaque aluminium leaf in the moving 

 system of the relay allows more or less light according to the current density prevailing to pass 

 through a triangular diaphragm on to the photographic film, the latter being developed after completely 

 passing the diaphragm. Tue apparatus works in subdued daylight. The movements of the light relay 

 are followed by mean-* of an observing tube (see Fig. B) and a reflecting mirror. In the foreground of 

 Pig. A, to the right, is shown the table with the transmitting apparatus and, in the background, to the 

 left, the table with the receiving apparatus. Fig. B contains simply the table with the receiving apparatus 

 completely fitted up, Figs. C and D show (in actual size) the reproduction of two tele-photographs made 

 with the demonstration apparatus. In the case of the demonstration apparatus the transmitting table 

 is placed immediately alongside the receiving table. 



The apparatus must only be used for demonstration purposes. A complete description will be sent 

 if desired. 



li:.', (iii8. Two Protecting Cases, frame of polished wood, glazed, doors and detachable tops, 

 cf. Fig. 02 067 A 



(i2,o<;<). Spare Selenium Cell 



<>2,07o. Diapositives of Tele-photographs 



(i2,071. Baretter Set after BC'la Gati, for measuring telephone and high frequency currents, 

 built into portable mahogany case 



T, e Baretters a v e fine wires of high temperature coefficient, being heated by the currents to be 

 measured. Their change in resistance, which gives a measure for the current, is measured by the bridge 

 connections of the Baretter set. In this manner it is possible to measure weak alternating currents, e. g. 

 telephone currents, by means of a portable moving coil pointer galvanometer. 



fii'. 072. Baretters of Platinum or Gold, without vacuum, 0.002 mm diameter quoted for on 

 application. 



i;2.07.'i. Baretter of thin wire or in evacuated vessel. Price according to sensitivity 2. 0. to 



D2.071. Moving Coil Pointer Galvanometer for above, 1 degree = 0.000,000,1. amp., for maxi- 

 mum sensitivity 



This instrument requires a perfectly steady base. 



ti2.i>7r>. Moving Coil Pointer Galvanometer for above, 1 = 0.000,001 amp., sufficient for 

 most purposes, also for use on ships 



<;2.n7(i. 2 Measuring Accumulators for above, built into wood case 



Condensers. 



For Condensers for Electrostatic Measurements, see pp. 833 834. 



\Vc supply two patterns of condensers for galvanic measurements. Our precision 

 condensers are intended for accurate measurements, having as dielectric first-quality 

 mica, the constant being scrupulously determined in our laboratory; their capacity is 

 constant and the insulation excellent. 



For technical purposes, in which the maximum accuracy is not necessary. \ve can 

 recommend our paraffin-paper condensers, which can stand voltages up to about .'500. 

 The paper condensers are calibrated accurately to within about !<>",, and the exact 

 capacity is stilted on delivery. 



Precision Condensers with mica dielectric, with one section, Figure. 



List No, 62,077 62,080 62,081 62,082 



Capacity, mfds. 0.01 0.1 o.r> 1 



l 4. 0. 4. 10. 8. 0. 10. 0. 



4. 15. 



2. 15. 

 0. 1.0 



14. 0.0 



2. 10. (I 



10. 0. (I 



10. 



2. 



0. 

 ;-.. O 



Cl. 2523. 



