... discuss? Trends in teaching mathematics to children The use of mathematics in child psychology The development of mathematical ability in children The fundamental concepts of mathematcis that children ... Strowger's switchboard find application in long-distance lines? It could carry connections through cable extensions It could handle a large volume of simultaneous calls It required the caller to activate ... the electronic switch system to about 10 per cent of that of the original Crossbar switching, installed in terminals in 1938, operated on the principle of an electromagnetic force, which rotated...