The 1st generation Apple Watch (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 features a new linear actuator hardware from Apple called the "Taptic Engine", providing realistic haptic feedback when an alert or a notification is received, and is used for other purposes by certain apps. The watch is equipped with a built-in heart rate sensor, which uses both infrared and visible-light LEDs and photodiodes.
