It will gain a fixed-line arm, but that is no recompense for what it will give up: its lock on the massive mobile market, encompassing two-thirds of Chinese customers and an even higher share of new subscribers.

ECONOMIST: Telecoms in China

The general wisdom when deciding between an ARM and a fixed jumbo is the same as with any mortgage, Mr. Gumbinger said.

WSJ: Fixed-Rate Jumbo Mortgages Make a Comeback

Given that 15-and 30-year fixed mortgage rates are at a historic low, why even consider an ARM?

FORBES: Why You Should Get An ARM

The biggest savings come if you pay off the loan within the five to seven years before the ARM adjusts--effectively turning it into a very short, very low-rate fixed mortgage.

FORBES

That said, as fixed-line voice telephony becomes a low-growth commodity, it is Sprint's mobile-phone arm and its 4m subscribers that must seem irresistible to Mr Ebbers, especially in the wake of last week's deal to unite the American wireless assets of Vodafone AirTouch with Bell Atlantic's mobile business.

ECONOMIST: The telecoms end-game