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Hitachi J100 adjustable frequency drive chassis.Most electronic appliances, such as receivers, are constructed from combinations of a few types of basic circuits. Analog circuits use a continuous range of voltage as opposed to discrete levels as in digital circuits.The number of different analog circuits so far devised is huge, especially because a 'circuit' can be defined as anything from a single component, to systems containing thousands of components.

Analog circuits are sometimes called although many non-linear effects are used in analog circuits such as mixers, modulators, etc. Good examples of analog circuits include vacuum tube and transistor amplifiers, operational amplifiers and oscillators.Some analog circuitry these days may use digital or even microprocessor techniques to improve upon the basic performance of the circuit. This type of circuit is usually called "mixed signal."

Sometimes it may be difficult to differentiate between analog and digital circuits as they have elements of both linear and non-linear operation. An example is the comparator which takes in a continuous range of voltage but puts out only one of two levels as in a digital circuit. Similarly, an overdriven transistor amplifier can take on the characteristics of a controlled having essentially two levels of output. Nevertheless, some states have long retained powerful upper houses. For example, the consent of the upper house to legislation may be necessary (though, as noted above, this seldom extends to budgetary measures).

Constitutional arrangements of states with powerful upper houses usually include a means to resolve situations where the two houses are at odds with each other.In recent times, Parliamentary systems have witnessed a trend towards weakening the powers of upper houses relative to their lower counterparts. Some upper houses have been abolished completely (see below); others have had their powers reduced by constitutional or legislative amendments. Also, conventions often exist that the upper house ought not to obstruct the business of government for frivolous or merely partisan reasons. These conventions have tended to harden with passage of time.