The first office capable of international direct distance dialing (IDDD) in the United States was the LT-1 exchange on the 10th floor of the 435 West 50th Street exchange building in Manhattan, New York. A group of its MF senders was equipped for the unique dual outpulse requirements of that service. Most large new urban 5XB in subsequent years had IDDD, and it was retrofitted to some existing ones, but most omitted the dual outpulse capability, that job being handled by TSPS.