depends on the purpose of the device
Light.
synapes
Different types of information are transmitted from one place to another by signals of light pulses through optical fibers.
stimuli are converted into electronic signals. Such electronic signals travel by a huge network of nerves throughout the body. These signals converge to the brain, where sensory neurons interpret them and send back an "order" through the Central Nervous System, to the correspondent point of the body where the stimulus has happened. Such "order" may refer to the release of defence cells, or simply tell your arm to touch the point of the stimulus,in order to calm you down, as a simple example. The signal that flows through the nerve, uses a mineral, magnesium, as a basis to conduct the electronic signal. Sodium is another mineral that participates of the process. Such travel may take only miliseconds to reach the brain and to come back.
The endocrine system is a system of glands that secrete hormones (made of proteins) into the blood stream. Once in the blood, these hormones bind to other protein called receptors in the membranes of the target cells. This is how signals are transmitted
The nerves that transmit messages from the rods and cones are called optic nerves. Rods and cones are specialized cells in the retina of the eye that detect light and convert it into electrical signals. These signals are then transmitted through the optic nerves to the brain, where they are processed and interpreted as visual information.
Light.
synapes
They are pheromones.
Different types of information are transmitted from one place to another by signals of light pulses through optical fibers.
stimuli are converted into electronic signals. Such electronic signals travel by a huge network of nerves throughout the body. These signals converge to the brain, where sensory neurons interpret them and send back an "order" through the Central Nervous System, to the correspondent point of the body where the stimulus has happened. Such "order" may refer to the release of defence cells, or simply tell your arm to touch the point of the stimulus,in order to calm you down, as a simple example. The signal that flows through the nerve, uses a mineral, magnesium, as a basis to conduct the electronic signal. Sodium is another mineral that participates of the process. Such travel may take only miliseconds to reach the brain and to come back.
telephone
It is a microphone or a telephone.
The transmission characteristic of a fiber optic channel is highly non-linear. It makes it a very bad medium for analog signals. Luckily it doesn't interfere with digital transmissions.
An electric siren is based on the principal of electrical energy and signals being converted into sound. Electrical inputs enter the a speaker through circuitry. In turn these signals are vibrate the air through the speakers function. Electrical sirens are in fact speakers, but there are mechanical sirens which use motion to drive the sound making assembly.
Electronic media history traces back to the invention of the telegraph in the 19th century, which enabled long-distance communication through electrical signals. The evolution continued with the invention of radio, television, and the internet, shaping how information and entertainment are transmitted and consumed. Today, electronic media plays a crucial role in shaping culture, politics, and society worldwide.
Satellite TV Providers transmits the signals through their satellite dish converting it first from digital signals to analog signals. These signals which were converted will be transmitted to the satellite. The satellite will then transmit the analog signals per request of the satellite dish connected to the receiver of the subscriber. Once signals are received, it will be converted back to digital signals which can be read by the receiver and be displayed to the television.
Sound is usually an acoustical wave in air. When this is converted e.g. by a microphone to an electrical voltage that can be sent through a wire. An amplifier and a loudspeaker can convert this audio signal back to an acoustical wave, you can listen to.