Printer Sharing Attachment for Personal Computer
Original Publication Date: 1985-Feb-01
Included in the Prior Art Database: 2005-Feb-18
The figure illustrates an attachment device which allows four host data processing systems to share one letter-quality printer. The attachment is suitable for connecting, for example, four IBM Personal Computers (PCs) to an IBM Type 5218 A03/A04 printer. The device, as shown in the figure, comprises five current loop driver/receive circuits 10, four of which are associated with the host PCs 11 and one of which is associated with the printer 12, a microprocessor 13, a 4-to-1 multiplexor 14, and a 1-to-4 demultiplexer 15. An inverter module 16 is associated with the port line 18 of processor 13. The current loop driver/receiver circuits 10 are similar to those used on the Type 5218 A03/A04 printer. It is a push-pull-type circuit which is capable of driving a long cable and is relatively immune to EMC noise.