The following may be of some help- In IPC-T-50F, "Terms and Definitions for Interconnecting and Packaging Electronic Circuits" Impedance- "The resistance to flow of current, represented by an electrical network of combined resistance, capacitance and inductance reaction, in a conductor as seen by an AC source of varying time voltage. The umit of measure is ohms." In C.A. Harper's and M. B. Miller's "Electronic Packaging, Microelectronics, and Interconnection Dictionary", McGraw Hill (1993), lib. call no. TK7804.H34 1993. "Impedance- the total opposition that a circuit offers to the flow of alternating current or any other varying current at a particular frequency. It is a combination of resistance R and reactance X, measured in ohms and designated by Z Z = sqrt(R^2 + X^2) "{square root of the sum of the squares} See also "Cnrolled-impedance Cable" and "Impedance Match" definitions in Harper and Miller. ______________________________ Forward Header __________________________________ Subject: Controlled Impedance Author: [log in to unmask] at _internet Date: 7/7/95 12:31 PM Does anyone out there have a simple, non-technical definition of controlled impedance? We are having some difficulty explaining satisfactorily to some management types. Thanks, Bob Smith [log in to unmask]