▁tend ▁to ▁stay ▁at ▁its ▁setting . ▁While ▁these ▁old ▁purely ▁mechanical ▁designs ▁did ▁have ▁some ▁fr iction , ▁the ▁return ▁spring ▁force ▁was ▁always ▁designed ▁to ▁overcome ▁this ▁fr iction ▁with ▁a ▁considerable ▁safety ▁margin . ▁The ▁return ▁spring ▁force ▁ens ured ▁that ▁thro tt le ▁returned ▁to ▁zero ▁if ▁the ▁ped al ▁force ▁applied ▁by ▁the ▁driver ▁was ▁reduced ▁or ▁removed . ▁ ▁With ▁electronic ▁acceler ator ▁ped als , ▁there ▁was ▁little ▁inher ent ▁fr iction ▁because ▁of ▁the ▁simplicity ▁of ▁the ▁mechanical ▁design . ▁The ▁tact ile ▁ped al ▁response ▁of ▁only ▁a ▁spring ▁force ▁with ▁no ▁h yst er esis ▁can ▁make ▁it ▁more ▁difficult ▁for ▁a ▁driver ▁to ▁maintain ▁an ▁acceler ator ▁ped al ▁position . ▁Man ufact ur ers ▁of ▁electronic ▁acceler ator ▁ped als ▁designed ▁their ▁ped als ▁with ▁additional ▁parts ▁to ▁re create ▁the ▁tact ile ▁response ▁of ▁the ▁older ▁mechanical ▁acceler ator ▁ped als . ▁To ▁quote ▁from ▁C TS ▁Corporation ' s ▁ 2 0 0 4 ▁US ▁pat ent ▁application : ▁ ▁... dri vers ▁generally ▁prefer ▁the ▁feel , ▁i . e ., ▁the ▁tact ile ▁response , ▁of ▁conventional ▁cable - dri ven ▁thro tt le ▁systems . ▁Design ers ▁have ▁therefore ▁attempted ▁to ▁address ▁this ▁preference ▁with ▁mechan isms ▁for ▁em ulating ▁the ▁tact ile ▁response ▁of ▁cable - dri ven ▁acceler ator ▁ped als . ▁ ▁The ▁Toy ota ▁electronic ▁acceler ator ▁ped als ▁contain ▁a ▁special ▁fr iction ▁device ▁made ▁of ▁n yl on ▁ 4