The term "shock collar" is out of date. Today the proper term is Electronic Collar. Assuming of course it's not an old fashioned collar that does nothing but shock and has a limited range of stimulus. Modern collars use electonic stimulous but the most advanced also offer tone and page (vibrate) options.
Safety and effectiveness of modem electronic training devices are supported by the Humane Society of the United States, the American Society for the Prevention of Cruelty to Animals (ASPCA) and the International Association of Canine Professionals, among others.
From: http://www.friendsofk9.com/documents/The_Facts_About_Modern_Electronic_Training_Devices .pdf
]The Facts about Modern Electronic Training Devices
Today's technology is surprisingly subtle, more effective[/url]