Clock source quality level. Options: 1. qlPRC(2) - primary reference clock 2. qlSsuA(4) - indicates that the clock signal comes from class I or class V sub-clock stipulated in G.812 protocol 3. qlSsuB(8) - indicates that the clock signal comes from class VI sub-clock stipulated in G.812 protocol 4. qlSEC(11) - indicates that The clock signal comes from SEC(SDH Equipment Clock) stipulated in G.813 protocol 5. qlDNU(15) - indicates that the clock signal can't be used for synchronization