8P8C

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El de 4 fils és el RJ9 o 4p4c que s'empra als microtelèfons y al teclat del MAC

4P4C o RJ-9

The 4P4C connector is the standard modular connector used on both ends of telephone handset cords, and is therefore often called a handset connector.^[4]

This handset connector is not a registered jack, because it was not intended to connect directly to the telephone lines. However it is often referred to as RJ9, RJ10, or RJ22.

Handset wiring[edit source | edit]

Handsets and often headsets for use with telephones commonly use a 4P4C connector. The two center pins are commonly used for the receiver, and the outer pins connect the transmitter, so that a reversal of pin connection is unaffected. Standard handset receivers functions normally when their polarity is reversed, but the electret microphone transmitter used in most modern handsets may not. Many telephones include polarity protection, so that the polarity may be reversed without affecting operation. Old handsets manufactured before 1985 using a carbon microphone transmitter are not sensitive to polarity. Some hands-free headsets also may have a 4P4C connector, but the wiring may differ from the above diagram.

Data port[edit source | edit]

The Macintosh 128K, Macintosh 512K and Macintosh Plus from Apple used 4P4C connectors to connect the keyboard to the main computer housing. The connector provided power to the keyboard on the outer two contacts and received data signals on the inner pair. The cable between the computer and the keyboard was a coiled cord with an appearance very similar to a telephone handset cable.^[5] The connector wiring, however, required a polarized straight through pinout. Using a telephone handset cable instead of the supplied cable could short out the +5 volt DC supply and damage the computer or the keyboard.^[6]

Some consumer equipment such as DirecTV set top boxes include a 4P4C low-speed data port connector.^[7] Such connectors can be adapted for use with a computer's serial port so that control commands can be sent from the computer to the set top box.

6P4C o RJ-11