dynamic reconfiguration of t1 access channels to various nodal services can be realized by applying carefully devised trunk - conditioning signals to disconnected channels to provide proper system responses and prevent billing errors as well as unwanted alarm conditions . trunk - conditioning with specific signals in binary sequences are defined for terminal lines and private branch exchange lines for the popular signalling type of e & amp ; m , ls , gs and plar . a steady idle signal is recommended for terminal line conditioning ; and a short duration of idle signal followed by a steady busy signal for inter - switch applications while loss of connectivity exists . this technique can be used in implementing the rina service function for services offered by at & amp ; t and any similar service provider . the service function will allow for greater access flexibility and better utilization of access bandwidth as well as network services . it is a value added feature to special services , as well as other existing service offerings .