How are the male and female terminals removed and replaced in a multipin connector?

I have four ESP-WROOM-32D boards, and four NRF24L01 modules. Each ESP-WROOM-32D board is connected to one NRF24L01 module. I want one NRF24L01 module to send a "Hello" message to the other three NRF24L01 modules at the same time. What is a good starter code in Arduino IDE?

It is often desirable in designing an electric wiring system to be able to control a single appliance from two or more locations, for example, to control a lighting fixture from both the top and bottom of a stairwell. In home wiring systems, this type of control is implemented with three-way and four-way switches. A three-way switch is a three-terminal, two-position switch, and a four-way switch is a fourterminal,two-position switch. The switches are shown schematically in P2.40(a), which illustrates a three-way switch, and 2.40(b), which illustrates a four-way switch. If the lamp (appliance) is to be controlled from more than twolocations, four-way switches are used in conjunction with twothree-way switches. One four-way switch is required for eachlocation in excess of two. Show how one four-way switch plus twothree-way switches can be connected between a and b in P2.40(c) to control the lamp from three locations. (Hint: The fourwayswitch is placed between the three-way switches.)

A common objective when manufacturing printed circuit boards (PCBs) is O a. maximizing the number of drill bit changes. O b. maximizing the number of holes drilled. c. minimizing the total distance the drill bit must be moved. O d. minimizing the number of holes drilled.

Conductors of dissimilar metals shall not be intermixed in a terminal or splicing connector.Please explain me why.

Explain 4x1 multiplexer? What is the difference between 2x1?

What are electrical techniques used for failure analysis