CONTACT WORK PHONE NUMBER (431)    HL7 FIELD (771.1)

This field returns the work telephone number of the contact from the
eleventh piece of the corresponding PATIENT file node and is dependent
on CONTACT TYPE field.  Please refer to Table (A) in the CONTACT TYPE
field.  The data will be returned in HL7 TN (Telephone Number) format as
follows [(999)999-9999X888].  The optional 'X' portion gives an extension.