The minijack 3.5mm is a popular connector used primarily for headphones although its functionality is much more varied.

It consists of a maximum of three connecting parts being the largest so-called mass or negative polarity and two of smaller size and located farther end of the connector, called living or positive that correspond to each channel, such three-part plug can transmit signals in two different channels, also known as stereo signals. It also exists in a mono minijack but version composed of only two parts, a body and a living or positive.

Flash system Canon EOS Inc. - Is the photographic flash mechanism used in Canon EOS SLR cameras, either film or digital 135. The main technologies are known by the names "A-TTL" "E-TTL" and "E-TTL II". These technologies have evolved both in the bodies of EOS cameras and flash units, which are sold under the brand Speedlite.

We can find 3 types of jack connector, monaural TS connector (tip-sleeve), TRS (tip-ring-sleeve) and TRRS stereo plug (tip-ring-ring-sleeve) which is used in most mobile devices, tablets, MP3 etc ...
We can difference these 3 types of connectors according to their diameter:

1. 6.35 mm jack connector or TS.
2. 3.5mm minijack connector or TRS, is the most common, usually used in headphone's output of portable devices.
3. 2.5mm jack connector or TRRS.

It consists of a maximum of three connecting parts being called the largest mass or negative polarity and two smaller size located more towards the end of the connector,
The called positive that correspond to each channel, such three-part plug can transmit signals in two separate channels, also known as stereo signals. There's a mono version, consisting of only two parts, a negative and a positive.

A. Protector
B. Stem
C. Ring
D. Tip
E. Kindred
F. Ring (Signal Right)
G. Tip (Signal Left)

Within the wide range of batteries on the market we can differentiate two large groups, disposable batteries and rechargeable batteries.
Disposable batteries are those that only allow a single use and when they are exhausted they can not be recharged. These batteries can store their energy for years.

Rechargeable batteries are those that can be recharged once exhausted. This type is losing charge when they are storedaccording to voltage. The most common we can find them of 1.2V and 3.7V

As a last point you have to take into account that lithium batteries, Lipo, Life etc. Due to its composition, specific loaders should be used.