308 JOURNAL OF THE WASHINGTON ACADEMY OF SCIENCES VOL. 11, NO. 13 



attracted to the relay magnet before it gets far enough away to make the 

 outer, pen-controlHng, contact. Thus, during a long dash signal the 

 relay armature simply chatters against the rear contact, without at 

 any time moving far enough to make the outer one. It is clear, there- 

 fore, that during the arrival of the signal the relay armature is chat- 

 tering against the rear contact and between signals it rests against 

 the front one. 



Figure 4 shows the front contact of the telegraph relay normally 

 held closed by the tension spring. The starting of local oscillations 

 causes the relay to operate in the manner previously described, the 

 front contact opens and the rear one closes. The opening of the 

 front contact operates the chronograph pen, and the closing of the 

 rear one short-circuits the oscillation-choking coil. The making of 

 the rear contact, therefore, stops the oscillations, causes the plate cur- 

 rent to fall back to the non-oscillatory value, the relay to release and 

 the front contact to close. 



If a continuous dash signal is being received the local oscillations 

 build up as soon as the relay armature leaves the rear contact, and it 

 is drawn back before the front contact is remade. Thus the chrono- 

 graph pen continues in the released position until the signal stops long 

 enough for the relay armature to remake the front contact. With no 

 signal coming in, the front contact of the relay is closed and the 

 chronograph magnet is energized. The pen-carrying armature is, 

 therefore, held against the inner stop. When the incoming signal 

 begins, the front contact is opened, the chronograph magnet is de- 

 energized and the pen-carrying armature is released against the outer 

 stop. It remains against the outer stop until the front contact of the 

 plate circuit relay is again made. The pen then returns to its initial 

 position against the inner stop. 



In the recorder design now in use, a single stage of radio frequency 

 amplification is provided so that the signal oscillations may be ampli- 

 fied before being applied to the grid of the tube in the regenerative 

 circuit. This preliminary stage of amplification increases the over- 

 all sensitivity somewhat, but the regenerative circuit itself and the 

 manner of its use account for all but a few per cent of the total sensi- 

 tivity attained. 



The preceding account describes a complete mechanism for recording 

 radio signals. A similar recording system has recently been described 

 by Captain L. B. Turner-. His methods of stopping the local oscil- 



2 The Electrician 83: 4. July 1919. 



