LONDON — A German subsidiary of European missile manufacturer MBDA has successfully tested technology which could deliver a “dial-a-yield” capability to conventional weapons.

Yield to maturity is the total return paid by a bond's expiration date, but the buyer of a callable bond also needs to estimate its yield to call.

The fate of the income investor is well-known at this point. Yields on 10- and 30-year Treasuries have been flirting with multi-decade lows in recent weeks and in an environment of depressed ...