It defines an electrical service to be any part of the distribution system from the primary circuit breaker to the first breaker, the main circuit breakers. (But not the emergency shut down system! This is not a law.) The definition of the distribution system does not include the distribution like plumbers use in the homes. It only covers the circuits connected to the power distribution like transformers, load detectors, etc.
There are three major types of electrical services under the law including distributed, single phase, and closed circuit. Distributed services include distribution with voltage and current controls, control of energizing circuits for all the utility loads like lighting and air conditioning. Single phase services are limited to a circuit only. Closed circuit systems are often used to provide more environmentally friendly means for the electrical services and also for heating and cooling. It can include one or several circuits. See more discussions from this article.
A Distributed Electrical Service has different parts including the breaker panel, the load detector, the utility wires that are carrying the high leg of 120 volts, and the single phase high voltage power supplies. The breaker panel is a flexible board placed over the high leg of the 120 volts. The load detector is the device that stops the power to the circuit when there is a short circuit. The utility wires carrying the high leg of the 120 volts are the utility wires to be attached to the electrical service panel.
In Single Phase Service, there is only one circuit breaker instead of three. It is controlled by a circuit switch or a voice coil. This type of electrical service has no utility wires to connect to any other appliance. For this reason, it can be easily installed and is very simple to use. It requires low installation costs and it is available in various models. You should then read more here!
Multi-circuit Panel is another form of electrical service panel. It has two to three single phase circuits on the outside and two to four circuits on the inside of the panel. When the circuit breakers to detect the short circuits, they stop the power from going to the appliance. If the appliance has both AC and DC input, then both the circuits are placed in the outer door of the service panel.
AC Couple is a special type of multi-circuit service panel where AC and DC input are possible. If both the input voltage of the AC devices are set to the same level, both the appliances will work. For this type of electrical panel, the wires are placed on the top of the outer door and the power shut offs are installed on the bottom of the outer door. When both the circuit breakers to detect a short, either one of the wires will be closed by the corresponding electric motor and the power will be disconnected from the device. See post too at https://www.britannica.com/browse/Electrical-Engineering/1.