A cellular extender works by picking up the signal of a Wireless Land Area Network, or WLAN, router and retransmitting it to its immediate surroundings. When the extender is stationed within the proximity of a WLAN router, it is able to send Wi-Fi signals to devices farther away from it.
Range extenders are helpful in allowing devices that cannot reasonably be situated very close to their router to receive a signal, but it should be noted that the signal they transmit is not as strong as the signal coming from the WLAN router. The result is that extender devices do not download content from the Internet as quickly, run streaming audio or video as quickly, or load data-rich pages as quickly as they would if they were close enough to draw their Wi-Fi signal from the WLAN router itself.
Multiple cellular extenders can be used in a chain to retransmit the WLAN signal multiple times and extend the signal even further than just one can, but there is inevitably an incremental drop in signal strength with each cellular extender used for this purpose.
Cellular extenders are subject to the same security protocols as other devices making use of a signal from a WLAN router, so if the signal is accessible only by way of a password, the extender also needs that same password entered in order to retransmit its signal.