supply of electronic l.c. gate telephone system, station telephone unit ( master telephone ) of electronic l.c. gate telephone system, with voice recorder & surge protection & line connection unit / circuit as per rdso spec no. rdso / spn / tc / 51-2021 ( rev.-1.0 ) with latest amendment / revision till the date of opening of tender. [ warranty period: 30 months after the date of delivery ] , gate telephone ( slave telephone ) of electronic l.c. gate telephone system, with voice recorder & surge protection & line connection unit / circuit as per rdso spec no. rdso / spn / tc / 51-2021 ( rev.-1.0 ) with latest amendment / revision till the date of opening of tender. [ warranty period: 30 months after the date of delivery ] , centralized power supply system ( 24+12vdc ) along with m.f. batteries of electronic l.c gate telephone systems with surge protection arrangements as per rdso spec no. rdso / spn / tc / 51-2021 ( rev.- 1.0 ) with latest amendment / revision till the date of opening of tender. . [ warranty period: 30 months after the date of delivery ]