Comprised of 24 channels, T1 lines can be used for a diverse number of applications. Commonly referred to as an integrated T1 or
channelized T1, this highly flexible circuit is designed
for businesses that need to run multiple services
over the same line. Common applications for
integrated T1 service include, Frame Relay/dedicated long
distance and Internet/point-to-point. Often confused with a
fractional T1, integrated service is made up of multiple
fractional T1 services.

--as quoted from Bandwidth Resource website

An Integrated T1 is a Dedicated T1 Line that shares Internet and Voice on the same T1 circuit. The 24 channels can be split up as phone lines and for internet use. When used for Internet Access, each channel is 64K max speed. The more channels used for Internet, the faster the internet will be. Integrated T1 is like Dedicated Voice Service in the respect that it uses the Dedicated T1 line. The difference is that in a Dedicated Voice T1 all the channels are used for Voice - whereas in an Integrated T1 line, some channels are used for Internet and the others are used for phone service. It is possible to have, for example, half of the channels used for phone lines and the other half used for Internet. Each channel can fill up to 64K of Internet Access, so that if your Integrated T1 is half voice and half internet, you would end up with 12 phone lines and 12 internet channels (64x12=768K internet bandwidth). Generally the Integrated T1 was created to save money. Therefore an office need not have to buy a Voice T1 and also a Internet T1 seperately, they can get it all on one line and spend half the money.