Tremolo is a modulation effect that imposes a rhythmic change in volume of sound. Once discovered in electric amplifier circuits, sound engineers and composers like the Baroque now use this low frequency oscillating modulation technique to create emotional piercing effect on their audience to maintain focus.
The low frequency tremolo can be gotten from the vibrating string in guitars, violins etc, and vocal sound, it is also produced from electronic devices created for its purpose. they are called optical tremolo.
Hardware security module is a Physical digital device that comes as a plug-in adapter used to secure and manage digital keys and provides crypto processing for strong authentication.
It has an onboard cryptographic keyboard and one or more crypto processors, and can be used on computers and network servers to prevent logical or physical authentication access to unauthorized users. It supports symmetric and asymmetric cryptography.
The answer is Tablets. It is a portable personal computer, generally with a mobile operating system and LCD touchscreen display processing circuitry, and a rechargeable battery in a single thin, flat package. It is bigger than smartphones.