ECONOMICS OF TELEPHONE Ki:i,\V Al'l'LICA TIONS 239 



Relays per mark(M- fund ion = ir — 2, 



c, = 0.01. 



TluMi A'aluc JXM- millisecond per relay is 



_ 0.04 X 0.25 _ 

 '" " O.OOOG X 2 " ^^"^'^- 



In this case, too, it is worth a considerable manufacturing cost penalty 

 to shorten the functioning time of the relay. 



(c) Relay Involved in a Suhevent — Release 



A particularly common form of subevent is the release of numerous 

 relay's at the end of one phase of marker action. In this case, assume 

 \'alues of the constants are: 



No. of markers per line = p = 0.0006. 

 Path factor = q ^ 0.02. 

 Relays per marker function = w = 5. 



Ct = $0.04. 



Then \'alue per millisecond per relay is 



0.04X0.02 



Cr = = $0,266 



0.0006 X 5 



Thus even in this case, an appreciable first cost value is associated with 

 the releasing speed of each relay. 



1.5 REVIEW OF EQUIVALENT FIRST COST EXPRESSIONS 



The pre\'ious sections have shown how some of the variable portions 

 of the relay design that affect its performance may be stated in terms of 

 first cost. Likewise methods are given for evaluating sensitivity and 

 speed performance in the same terms. These may be summarized as 



Cost of a coil : 



Cw = CnR + CnN. (1) 



Cost of an item as a function of demand: 



n 2n n 



