PLASTIC MATERIALS IN TELEPHONE USE 



495 



Phenol Fabric 



Phenol fabric is similar to phenol fiber except that it is made with 



fabric instead of paper. It is generally used for its mechanical strength 



since its electrical properties are inferior to fiber. Phenol fabric is 



used in tools where high strength and resistance to impact and bending 



— NOTES — 

 ARCING BRUSH AND ADJUSTABLE 

 SIGNAL BRUSH ARE SHOWN IN 

 PROPER POSITION FOR START OF A 

 TEST WITH ARCING BRUSH JUST 

 BREAKING AND SIGNAL BRUSH 

 JUST MAKING 



IN THIS POSITION THE POINTER 

 SHOULD BE AT 90 DEGREES ON THE 

 PROTRACTOR SCALE 

 WHEN THESE ADJUSTMENTS HAVE 

 BEEN MADE ADVANCE PROTRACTOR 

 IN A CLOCKWISE DIRECTION 15 

 DEGREES FROM ORIGINAL SETTING 

 AND START THE TEST 



BANK OF 208-TYPE 

 RELAYS 

 208Bq 208Gr) 



B p Go 



PIGTAIL 

 CONNECTION 



HIGH-SENSITIVITY 

 RELAY 



+i 



APPROXIMATELY 

 no VOLTS DC 



Fig. 8 — Circuit for arc resistance test. 



are necessary, in terminal plates, cable terminals, gears and in general 

 where phenol fiber does not have suitable structural properties. 



Urea- Formaldehyde Plastics 

 Condensation products made from urea and formaldehyde have 

 attractive possibilities as thermosetting plastics. Relatively light- 



