If a port on a 16-port T1/E1 ASAP Adapter card, 32-port T1/E1 ASAP Adapter card, or 2-port OC3/STM1 Channelized Adapter card is configured for CESoPSN VLL service, failure of the VLL forces a failure of the associated DS0s (timeslots). Because there can be n ✕ DS0s bound to a CESoPSN VLL service as the attachment circuit, an alarm is propagated to the bound DS0s only. In order to emulate the failure, an "all 1s" or an "all 0s" signal is sent through the DS0s. The bit pattern can be configured to be either all 1s or all 0s. This is sometimes called "trunk conditioning".