This read-only DisplayString, up to 255 characters, is the human-readable text sent along with the wvIduHeartBit keep-alive trap, formatted to include the terminal's serial number and, depending on wvTrapKeepAliveVarsSelect, values such as RSL, BER, or UAS. An admin reading this string in the trap log gets a quick, self-contained summary of the terminal's identity and current health without needing to correlate a separate poll. For example, a wvTrapKeepAliveString reading "Serial Numbers: SN12345 RSL=-42 BER=1e-9 UAS=0" lets the admin immediately see, from the trap alone, which unit sent it and that it currently has good signal and zero unavailable seconds.