OSCILLOGRAPHS 



371 



A schematic diagram of the optical system of the recorder and of the 

 camera, as used in the polar oscillograph, is shown in Fig. 1. Some of 

 the mechanism essential for operation is omitted for the sake of 

 clearness. 



One of the calendar clocks used in conjunction with these oscillo- 

 graphs is shown with cover open in Fig. 2. A space is left below the 

 clock face for a card on which may be written identifying or other 

 information relative to records that may be obtained. Lamps are 

 mounted within the cover to illuminate the clock when necessary. 



OSCILLOGRAPH 

 CIRCUIT 



Fig. 3 — Circuit of high-speed line-relay. 



Both oscillographs are equipped with automatic devices which 

 enable them to make records of transients for which they are intended 

 without the attention of an operator. These automatic features will 

 be described in some detail in the following discussion of the individual 

 oscillographs. 



One part, however, a high-speed "line-relay" is common to both. 

 It consists of a pair of high-speed polar relays, the windings of which 

 may be connected into a line in such a way that, depending on the 

 polarity, one or the other will be operated by any pulse of sufficient 

 magnitude. The relays may be so biased that they operate only on 

 pulses in excess of any given magnitude. They are connected so that 

 when they do operate they remain operated until reset by some 

 external means. Contacts on the relays are connected to the apparatus 

 to be controlled so that a single positive or negative pulse will put that 



