** Spirent Communications SPT.L rises as much as 2.4% to 190p; among top pct gainers on FTSE 250 .FTMC index
** Electronics equipment maker Keysight Technologies KEYS.N signs deal with Viavi Solutions VIAV.O to sell SPT's high-speed ethernet and network security business lines
** KEYS, which outbid VIAV to buy Spirent for ~1.16 bln pounds ($1.46 bln ) last March, expects sale to complete shortly after SPT's acquisition becomes effective
** Stock gains more than 74% over past 12 months
($1 = 0.7928 pounds)
Spirent shares https://tmsnrt.rs/3XEVuK4
(Reporting by Aby Jose Koilparambil in Bengaluru)
((abyjose.koilparambil@thomsonreuters.com))