Microsoft has remained mum on the rumors that the Surface Phone will drop this year. The Redmond-based tech giant previously announced that it would stop supporting its current Windows 10 phones, but there are speculations that the Surface Phone is already next in line. In fact, a block of code from the upcoming Windows 10 build hints that the Surface Phone is actually under development. 

As reported by Ars Technica, the latest Windows 10 Insider Preview build was spotted to have new API codes for telephony features. These APIs are said to be required for a dual-screen Windows handset. With this, it is strongly speculated that the upcoming Windows update might have been designed to support the Microsoft Surface Phone, which has been tipped for the longest time to sport a dual display with seamless hinge. 

Specifically, the Windows 10 Insider Preview build 17650 includes API codes that are usually found on devices used for blocking phone calls, dialing numbers, and supporting Bluetooth headset connections. The APIs found on the Preview build also has video calling support, making video calls possible over cellular connectivity. To note, cellular connectivity was already featured via Windows 8 update, although the feature was mostly confined for data connections, citing the Surface Pro's LTE connectivity as an example.

On the other hand, the APIs spotted in the Windows 10 Insider Preview build is capable of handling voice-based calls, according to Digital Trends.

Earlier reports suggest that the Microsoft Surface Phone will be designed as a pocket personal computer with stylus support. Although, the Surface Phone will still have phone capabilities just like the usual handset. There is not much information about the Surface Phone's foldable design, although several patent leaks have already been published on the internet that explain how the device's folding mechanism will work.

Moreover, Microsoft is reportedly dealing with Qualcomm to introduce the Windows 10 operating system to ARM processors. This also raises the possibility that the partnership will make the Surface Phone powered by a Qualcomm chip, although an Intel-based device is still in the cards.