For photographers who shoot with strobes, the following information, found in Chuck Westfall’s Tech Tips column at The Digital Journalist, may be useful:

The trigger circuit voltage (TCV) rating for any EOS SLR is the same on the hot shoe as it is on the PC terminal (if the camera has one), but the acceptable TCV level varies according to the camera model. Incidentally, the main reason for the difference is the way the X-sync signal is generated. With the 250V cameras, the X-sync signal is generated electronically. With the 6V cameras, the X-sync signal is generated mechanically. There are no guarantees, but going forward I anticipate that most if not all future EOS SLRs will be safe for TCV up to 250 volts.

Canon Digital SLRs safe for TCV up to 250 volts:
EOS-1D Mark II N, EOS-1D Mark II, EOS-1Ds Mark II, EOS-1D, EOS-1Ds
EOS 30D, 20D, 5D
EOS Digital Rebel XTi, XT (400D/350D)
EOS D6000/D2000, Kodak DCS560/DCS520 (circa 1998)
EOS-DCS series (circa 1995)

Canon Digital SLRs safe for TCV up to 6 volts:
EOS 10D, D60, D30
EOS Digital Rebel (300D)

Canon 35mm SLRs safe for TCV up to 250 volts:
EOS-1V, EOS-1N, EOS-1, EOS 3

Canon 35mm and IX240 SLRs safe for TCV up to 6 volts:
EOS 650, 620, 630, RT
EOS 850, 750, 700
EOS Rebel Series
EOS Elan Series
EOS 10s, A2E, A2
EOS IX, IX Lite
T90

Canon SLRs released earlier than the T90 did not have TTL flash circuits, and comprehensive information on safe TCV levels is not available.