RCA Jack

It’s widely used in analog signal transmission. The simple structure design is from the long history.
Until today, it’s still used in master tape machine, vinyl record machine, CD player, Mixer, effects unit, amplifier, and so on. 
RCA socket's structural section is a standard coaxial design although there is no standard characteristic impedance but sometimes it is used for other RF terminal adapter interface, and to delivery composite video signals (the appearance is orange), or S/PDIF format digital audio signal.  

In the analog signal transmission, the left channel’s appearance is red color and the right channel’s appearance is white or black color.
For the interface of RCA jack, the positive pole is hidden in the body. The inner diameter is about 3.175mm (1/8”).
The outer larger body or the shell is the negative pole. The inner diameter is about 8.25mm (1/3”).
There is insulator between the positive pole and negative pole to isolate the insulation material.  

RCA jack are divided into 3 types: Cable mount, Case mount, and PCB mount. 

廣泛應用於類比訊號傳輸，發展歷史長久及結構簡單的設計，迄今仍被應用於
母帶機、唱盤機、光碟撥播放器、混音器、效果器、擴大機及主動式揚聲器等設備。
僅管沒有標準的特性阻抗，但RCA端子在斷面結構上是屬於相當標準的同軸設計，
故有時仍被採用作為其他RF端子的轉接介面，用以傳遞數位訊號，
​如應用於複合視訊訊號(外觀為黃色)或S/PDIF格式的數位音頻訊號(外觀為橘色)。

RCA母座在傳遞類比訊號時，左聲道外觀為紅色，右聲道外觀為白色或黑色。
在介面部分，正極隱藏於本體之內，容許內徑約為3.175mm(1/8")，
外部較大的本體為負極，外徑約為8.25mm(1/3")，兩者之間以絕緣材質隔離，

母座在分類上大致可區分為線材按裝、機殼按裝及PCB按裝。