be applied as in (liiect-ciirieiit-prolilenis. Foi' iiislaiice two parallel 



resistances z, and z^ mav be replaced b_v one single resistance ^-— — ^ • 



z, [ z. 



If there are also inu(nal inductions M, in the system, tlie left-hand 



part of (J 2; is to be coni|)leted by terms of the form Ji),\I,A,. In 



that case the method of complex resistances is still applicable though 



the analogy with direct-curi-eut-problenis now does not hold entirely. 



We shall now apply the methoil to the audion. By a system of 

 self-inductions, capacities and resistances the anode is connected with 

 the kathode; the grid is coupled witli this circuit either by a direct 

 contact, or by means of one or more mutual inductions. Further 

 there are two batteries in the system, which provide for the mean 

 lensions e and r being such that we aie operating at the proper 

 point of the chaiacteristics (e.g. I> in tig. 3). For alternating currents 

 the batteries behave as ordinary resistances. Since we ai-e only 

 concerned with the alternating currents and tensions we shall lience- 

 fortli for the sake of convenience omit the indices to these (piantities. 

 (See e.g. (lOj). 



Hence we obtain for the audion a same set of equations as (11). 

 hjcospt now having the value /r, where r is the alternating part 

 of the grid-potential. These can again be reduced to a set of equations 

 (12). The grid-potential, however, in its turn is a function of the 

 currents in the anode-circuit. Hence (12) is to be completed by one 

 equation of the form : 



E — X ^ B, A, . . . . . . . . (13) 



where the /:i,.'s in general are comj)lex ([uantities. 



If for a given connection we can find a set of ^'s which satisfy 

 (12) and (13) for a real value of />, this connection has a generative 

 action. Many of such connections have been published in almost 

 confusing abundance. A summary is for instance given by Arm- 

 strong ') and by Eccles *). 



From the above we may deduce the following general rules for 

 the generative audion-connections : 



.4. If a connection is found, which gives alternating currents of 

 a definite frequency, we can deduce from it others, which give 

 currents of the same frequency by replacing the "alternating resis- 

 tances" by others which are eqinvalent for this frequency. In this 



') See Jahrb. I'. Dr. Tel. (1918) 12, p. 241. 

 ') Eleclrician July 1916. p. 573, Aug. 1916, p. 595. 

 See also: Yearbook of Wireless Tel. (1917) p. 674. 



