PSTN MODEM; DIN RAIL MOUNT; INDUSTRIAL TEMP OPERATING RANGE (-25 TO +70C);BELL 103;BELL 212; V.21;V.22;V.22 BIS;V.32;V.34;V.90; GALVANIC ISOLATION B/W COMMS PORT & PSU;CAN USE SC 23038 INSTEAD (HIGHER COST & WIDER);LIMITED AVAILABILITY OF PSTN MODEMS MEETING REQUIRED SPECIFICATIONS & INTEROPERABILITY; REFER APPROVAL FOR LIMITED SOURCING FOR DETAILS;ITEM REPLACES SC 18752;SC 23038 CAN BE USED TO SUSTITUTE FOR THIS