High Speed Current Interface Driver
Original Publication Date: 1978-May-01
Included in the Prior Art Database: 2005-Feb-20
A high speed, high voltage, isolated normally closed switch is provided having low radiated noise. In communications applications, it is useful to have a current mode of signal transmission to talk with teletypewriter terminals and other devices that use a similar electrical interface, but at a speed 50-100 times greater. The characteristics of the interface are: mark - current flow of 20 to 60 milliamps; space - no current open circuit voltage up to 150 volts. The circuit is in marking condition when no power is applied. For slower speed lines, these requirements are adequately met using the normally closed contacts on a relay.