The term OSNA is a USOC Term (Universal Service Ordering Code).
Typical designations are 63OSNA123456.
The first 2 digits determine the location where the circuit was engineered (63 in New York State is Syracuse).
OS stands for outside station, N is non data, and the A stands for ancillary equipment (not telco) connected to the circuit (like the pBX at one end and the phone or key equipment at the far end.
Gary


Gary