Simplex 740-683 — a Simplex 740-series service part number that appears in no published Simplex parts list.
The 740 prefix alone tells you nothing about what a part is. Simplex uses the block for items of completely different kinds: 740-748 is the MAPNET/IDNet Quad Isolator Software supplied as a programmed IC burned on a 246-320 blank 27C64 EPROM, while 740-673 and 740-674 are semi-flush trim bands, 740-828 to 740-849 RF shield kits, 740-769 a jumper plug kit and 740-836 a ferrite bead. The 4100/4100+/UT list explains the absence: firmware numbers for pre-programmed EPROMs are published in Field Service Bulletins, not in the parts list.
- Not listed in the 4100/4100+/UT, 4100U, 4100ES or 4020 service parts lists
- Pre-programmed EPROM numbers are published in FSB-252R, FSB-253R and FSB-348R
- 8.01 is a genuine Simplex designation, but it is a 4100/4020 system executive software revision level, not part of a part number; Rev 801 is that revision with the decimal dropped
- The only socketed EPROM Simplex documents on 4100 MAPNET II hardware is 740-748 at U11
Read the number off the part in the panel before ordering: 740-748 is the quad isolator programmed IC, 246-320 the blank EPROM.
