New update of Telegram for desktop (version 1.1.0) is now available from the Telegram website and through the inbuilt updater on the desktop app. Support for voice calls is the key feature in this update.
Telegram say voice calls are “secure, crystal-clear” and “constantly improved by artificial intelligence”. The calls are built upon the end-to-end encryption of Telegram's Secret Chats. By introduction of voice calls to its desktop apps Telegram becomes direct competitor to apps like Skype, where their primary focus is calls, unlike Telegram’s which is on messaging.
There are several other changes besides voice calling. Firstly, the new emoji, stickers, and saved GIFs panel takes up a separate space on the right when Telegram is open in a wide enough window. Secondly, chat admins can now delete messages sent by other members. Lastly, you can manage the blocked users list in your supergroups.
Telegram latest update is available on Android and iOS. Note that voice calls are not supported on Ubuntu Phone or in the Telegram web app.