While financial markets have become increasingly high-tech, they still rely on the oldest form of communication to get the job done.

The best example of this is the use of “voice brokers”, who act as middlemen for banks trading swaps and other fixed income securities in financial centers that link Asia, Europe and the U.S.

And these brokers, who have lately run afoul of the U.S. authorities, are now in the crosshairs of regulators investigating the possible manipulation of the Libor pricing benchmark regarding these swaps and many types of loans.

Read: UBS suspends traders in Libor scandal

Read how the Libor investigation has shone a light on the links between voice brokers and traders, and the shortcomings of the voice broker model.