Xov 63 379. 



Telephony and Microphony. 



1055 



63 374. 1:5. 



63370. 3:10. 



63378. 1:10. 



63 375. 1 : 5. 



63 379. 1 : 8. 



63.377. Model of a Micro-telephone Station, Figure, excellently adapted for demonstration 

 purposes . 



The model can be worked and gives good results. A microphone is built open upon a polished 

 baseplate, being fitted to two pillars and rotating about a horizontal axis. In addition the board is 

 fitted with all the necessary leads and terminals, an induction coil, the secondary winding of which 

 can be moved along a perpendicular slide so as to be able to vary the inductive action. 



In addition, two telephones pertain to the apparatus. One of these telephones is built in section 

 and can be taken to pieces to show the internal construction. Supplied with the apparatus is twelve 

 metres twin telephone flexible with pin ends. 



63.378. Model of a complete Telephone Installation, consisting of two stations, Figure, 

 very comprehensive and quite workable. The connections are in accordance with those 

 usually adopted in practice for domestic and factory installations 



s. d. 

 2.10.0 



7.10.0 



63,379. Apparatus for Telephonic Lecture Experiments, after Dr. Heilbrun, Figure (E. T. 

 Z., 1908, p. 341), with two different microphones, precision telephone, and a phono- 

 graph cylinder j 9. 0. 



The apparatus consists of a phonograph, the sound pin of this being connected with a microphone. 

 It is thus possible to transmit to some distance the musical selection, etc., contained on the record. 

 The apparatus is very well adapted also for demonstrating the difference in action of different micro- 

 phones and telephones. It is practicable to insert a galvanometer (preferably No. 61,528) in the circuit. 



Cl. 3070, 3074, 6127, 



3079, 

 3075, 5200. 



