A bias is a permanent magnet placed near a reed contact to oppose or aid its operation. Normally-closed reed contacts use a biasing magnet to oppose the actuating magnet. Latching reed contacts use a biasing magnet that aids and opposes the latch and unlatch operations by the actuating magnet.
In electronics, biasing is the setting of initial operating conditions (current and voltage) of an active device in an amplifier. Many electronic devices, such as diodes, transistors and vacuum tubes, whose function is processing time-varying (AC) signals, also require a steady (DC) current or voltage at their terminals to operate correctly. This current or voltage is a bias. The AC signal applied to them is superpositioned on this DC bias current or voltage.
The operating point of a device, also known as bias point, quiescent point, or Q-point, is the DC voltage or current at a specified terminal of an active device (a transistor or vacuum tube) with no input signal applied. A bias circuit is a portion of the device's circuit which supplies this steady current or voltage.