In message <34CF49B8.5E13165C@explorenet.net>, richard dellacona writes >hello out there does any one out there know why 60 cps and 120 vac >is used in usa for line voltage no one seems to know or have a good >answer for this question In the UK it's 50 Hz and 240 V AC single-phase or 440 V three-phase. Probably because 50/60 Hz was related to the optimum speed to run the generators, and produce a reasonably high-frequency supply, without stressing the moving parts too much. 120 V AC is probably optimum for reducing transmission losses, without stressing the insulation too much, and is reasonably safe from an electric shock point of view. You also have a 240 V supply in the US, I believe, derived from two 120 V lines. When I was young we had a DC mains supply. All engineering design is a compromise, ultimately. Leon -- Leon Heller: leon@lfheller.demon.co.uk http://www.lfheller.demon.co.uk Amateur Radio Callsign G1HSM Tel: +44 (0) 118 947 1424 See http://www.lfheller.demon.co.uk/dds.htm for details of my AD9850 DDS system. See " "/diy_dsp.htm for a simple DIY DSP ADSP-2104 system.