The Space Giants aka Ambassador Magma - Live Action DVD Video 2 of 3 (1966-67)
Episodes 19-36 of 52

A little boy blows a whistle once to call a 50-foot gold robot to fight monsters, two times to call his silver robot wife, or three times to call their rocket boy son.

Probably ripped from Japanese Laserdisc with English broadcast audio dubbed over.  Almost entirely in English, with some Japanese and silence.  Excellent video quality.  Compete with episode menu.

Check these pics to jog your memory of this show: http://www.coolstuffvideos.com/spacegiant.html

See also Ambassador Magma:
http://en.wikipedia.org/wiki/Ambassador_Magma