A programmable electronic sign, comprising:
- a set of individual character displays mounted in alignment to form a sign, each display having a plurality of illuminable segments which when selectively energized form an image of a selected character;
- a corresponding set of selectable programming cards each associated with a respective one of said displays, each card containing indicia designating the specific segments to be illuminated in the associated display to produce on that display a character defined by that card;
- means utilizing said set of programming cards and interconnected with said displays for energizing in each display only the segments specified by the associated program card, each display thereby containing an illuminated image of the defined character, the characters together forming a selected message;
- each of said programming cards contains a printed circuit having conductive strips corresponding to display segments to be illuminated, and wherein said means for energizing comprises;
- a respective socket for receiving and making electrical contact to each programming card in said set,
- a power source, and
- electrical interconnection means for connecting power from said source to each of said displays via the associated programming card and socket, so that for each display only the segments corresponding to said conductive strips in the associated programming card printed circuit are energized;
- said power source comprises rectifier means providing unfiltered, rectified ac power and wherein said electrical interconnection means includes a silicon controlled rectifier in circuit with each programming card, so that power is supplied to the display segments via that silicon controlled rectifier and the associated programming card printed circuit, and trigger means for providing a trigger signal to said silicon controlled rectifiers for substantially the entire duration of time that the characters selected by said programming cards are to be displayed, said silicon controlled rectifiers going off at the end of the ac half cycle next following termination of said trigger signal as said unfiltered power approaches ground potential;
- each of said displays comprises an n .times. m matrix of lamps, wherein
- said programming card printed circuit has a common contact and (n .times. m) other contact locations, said circuit having a conductive path extending from said common contact to those contact loctions corresponding to display segments to be illuminated,
- wherein said common contact is connected via said socket to a silicon controlled rectifier, all of the other contact locations being connected via said socket to respective segments of the associated display,
- a source of unfiltered, rectified ac power connected to all of said segments, said silicon controlled rectifier being in the return path to said source, so that when said silicon controlled rectifier is switched on, a power connection is completed via said silicon controlled rectifier, said common contact, and said programming card printed circuit to said corresponding display segments, and
- trigger means for providing a trigger signal to turn on said silicon controlled rectifier for a duration of time during which said display is to be illuminated, said silicon controlled rectifier being turned off after termination of said trigger signal the next time that said unfiltered power approaches ground potential.