Four pairs
A crossover cable reverses the signals at ends of the cable.
4 pairs of wires.
Whether you can buy wire connectors at local hardware stores depends on the hardware store. Some hardware stores do carry wire connectors.
One place a person can try is Amazon. Other options for cheap wire connectors are DasCheap, AliExpress, DHGate, Radio Shack, and APlusSupply. Or one can by second-hand wire connectors from eBay.
Yes RJ12 connectors are used to connect wire to dial up modem
Well, I would recommend disposing wire connectors to electronic disposal centers or areas. However, there is also the option of donating them to schools.
the magnetic field around the adjacent pairs of wire
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High Heat Porcelain Wire Connectors are very safe.
One can purchase electric wire connectors at retailers such as Lowes and Home Depot. One can also purchase them online on sites such as Amazon and eBay.
2 wire of pair
It depends on the type of 110 block.