When yields rise, the value of callable bond may not fall as much as that of a similar straight bond because of the embedded call option feature. With a decrease in interest rates, the value of a callable bond can increase to only approximately the call value (the call price serves as a cap or “ceiling.”). Straight bonds will continue to exhibit the inverse relationship between yields and prices, as there is no “ceiling” call price.
The statement that begins, “As interest rates decrease…,” should continue, “.. the value to the issuer of the call option increases.” As interest rates decrease, the issuer values the call option more because the company has the potential to call the bond and replace existing debt with lower-coupon (and thus lower cost) debt.