Apple Watch (original)

he first-generation Apple Watch,[69] colloquially referred to as Series 0, uses the single-core S1 system-on-chip. It does not have a built-in GPS chip, instead relying on a paired iPhone for location services. It uses a linear actuator called the "Taptic Engine" to provide haptic feedback when an alert or a notification is received, and is used for other purposes by certain apps.[14] The watch is equipped with a built-in heart rate sensor, which uses both infrared and visible-light LEDs and photodiodes.[70] All versions of the first-generation Apple Watch have 8 GB of storage; the operating system allows the user to store up to 2 GB of music and 75 MB of photos. When the Apple Watch is paired with an iPhone, all music on that iPhone is also available to be controlled and accessed from the Apple Watch.[71] Software support for the first Apple Watch ended with watchOS 4.3.2.

Source https://en.wikipedia.org/wiki/Apple_Watch#First_generation