annual maintenance contract for 11 nos. of modsonic make ultrasonic flaw detector,model: einstein - ii (at) machines and 01 no digital ultrasonic double rail tester, model:railscan-200w for the year 2021-22 & 2022-23 on single tender basis from m/s nvjelectronics & services, 103/ 20, foreshore road, howrah - 711102.bidding type normal tender .