online ups and offline ups
the two main types of communications are emailing and socialising
There are two types of MAC protocol. 1. Centralized 2. Distributed
letter E- Mail Phone Telegram SMS
talking and writing letters
There are two main types of communication. The first is verbal communication, which can take the form of speaking or writing. The second is non-verbal communication which can take the form of body language or tone of voice.
There are UPSs made with an automatic bypass switchthat when the main supply is stable bypasses the UPS and connects the device directly to the main supply. However these are more expensive than the kind that always runs power to the the device through the UPS, also the bypass switch is a break before make electromechanical relay. The "transfer time" of such a relay is measured in milliseconds and is often longer than one cycle of the main supply power. Thus when the main supply drops out power is lost to the device for this period before the bypass switch connects the device to the UPS. For some electronics this brief loss of power is no problem, but some electronics (particularly computers) cannot tolerate it.For computer UPSs it is thus generally safer to design them to always power the device from the UPS, not the main supply. Such UPSs are also sometimes called "zero transfer time UPSs".Another issue with UPSs is the shape of the AC waveform they deliver: many early inexpensive UPSs delivered squarewave AC, whereas more expensive UPSs delivered stepped pseudosinewave AC; certain devices (especially those with AC motors in them) could not tolerate this and would not function or in some cases were damaged. Thus the true sinewave UPS was developed, which of course was more expensive and more complicated than the other types. It is always important to buy a UPS that is compatible with the device it will power, false economy here will in the long run be more expensive.
the main types are: soprano and mezzo soprano
The 2 main types of timber are Softwoods and Hardwoods.
+ and -
The main types are endoskeletons and exoskeletons.
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Two main types of satellites are: Communication(s) Remote Sensing
crops and livestocks
The two main leaf types are simple and compound leaves. The main difference is in their surface areas and the shape edges.
LanD aNd WatER
earthquake and tsunami?
The main type of satellites are: 1) Geostationary 2) Polar