USB OTG(On The Go) came in late 2001. This specification allows typical USB devices such mobile phone to act host with standard USB socket such as USB flash drive, keyboard, mice and other devices which were supported them.
Use of USB On-The-Go allows those devices to switch back and forth between the roles of host and client devices. For instance, a mobile phone may read from removable media as the host device, but present itself as a USB Mass Storage Devices when connected to a host compute
The device controlling the link is called the master or host, while the other is called the slave or peripheral.
In early days USB OTG supported devices would need a extension cable.
This extension cable consisted of male micro USB and female usb standard.
Now as the smartphone was emerged and dominated all of the phone market. You can still use extension cable for a same function as their predecessor. Therefore USB - OTG has been coming again with another great innovation.
Type of USB
USB OTG have no wide spread among their popularity in first debut mainly because their function doesn't accommodated with old hardware host especially for old mobile phone like a Symbian Operating System.
In Their early days old hardware host doesn't need huge amount of resources. Their heavy load function was a far better if substituted by standard PC. That's why we rarely saw them in first places.
USB OTG in Smartphone Era
As the modern Smartphone is becoming more advanced and resources hungry. Now We can find USB OTG which was merged with USB flash drive.
USB OTG flash drive consisted of two different jack, Male Micro USB and Male Standard USB.
Male Micro USB acted as socket to the smartphone and Malestandard USB acted as socket to the PC.
USB OTG flash drive has a dual features by using both of sockets,
Main feature acted as standard USB flash drive. User can store files in the same manner as a Standard USB flash drive with non-supported OTG
Secondary feature by using a Male Micro - USB to connect onto smartphone Female Micro - USB socket.
USB - OTG flash drive will become an external storage by using second feature besides external Micro SD Card if any.
Smartphone can read or write data while using an USB OTG flash drive as external memory without need an external cable. Consider those particular data was supported by smartphone operating system.
By using USB OTG flash drive, it is very possible to store music, HD movie, or high resolution pictures from other computer and open them later on smartphone. Furthermore you can use internal memory efficiently by allocating them for more important tasks.
What You Should Know before buying USB OTG Flash Drive
Latest Smartphone from major manufacturers like a Android, Apple, Windows Phone, and Blackberry known for theirs USB OTG supported devices.
However many of them have a maximum storage limits for their system.
For the example if you have a brand "A" and their maximum storage was limited on 64 GB. You split it by two, a 32 GB for internal and other 32 GB for external purposes, then you can't add USB OTG flash drive for more external. Consequently, you should get removed a 32 GB external or replace it with a lower one.
Anyway some type of older devices like Samsung GT doesn't supported by USB - OTG flash drive.
You need to tamper on non-supported devices with something risky like a rooting for Android System to enabled USB OTG external memory function.
It is very not recommended if you didn't know anything about the system consider it might make your devices bricked or warranty lost. So Always check their specification for USB - OTG supported devices if you set a plan to buy regarding it.
And lastly If you have a plan to obtain Apple USB OTG flash drive always check first. Apple smartphone came with very different type of socket for their products.
Other(Black) Smartphone VS Apple(White) Smartphone jack