A call is queued off-hook if no B channel is free in any of the trunk groups. This results in a B channel being reserved for the station. An Off-Hook queue can likewise take place in a transit station (Node 1-89-200). If a B channel becomes free, this is assigned to the queued call/circuit with the highest priority.

If a direction (AMO LDAT) has been assigned to the parameter LATTR with the parameter value OHKQ, the call is inserted into the off-hook queue.

In the transit case, the LCOSV of the station must additionally be assigned the parameter value OHKQT, and the COT of the incoming circuit the parameter value OHKQ.