The prefix <tele> can bear the main stress of the word on its first syllable. The pronunciation of the prefix in this case is ˈteli. Here are some examples of this:
telegram telegraph telephone teleprinter telescope teletext televise
In some words, however, the first syllable of the prefix bears secondary stress and the pronunciation is ˌteli. Examples:
telegraphic telekinesis telepathic telescopic
The third possibility is that the second syllable of the prefix bears the main stress of the word. In this case the pronunciation is təˈle. Here are some words of this sort:
telegrapher telemetry telepathy telephony telescopy
The word television can be pronounced either as ˈtelivɪʒn or as ˌteliˈvɪʒn.
This tip is a joint production by Petr Rösel and John Maidment.