WIRE COMMUNICATION AIDS TO AIR TRA NSPORTAI'ION 473 



through all of the information to obtain the trend of weather at a 

 particular point. The tape machines are also somewhat smaller, less 

 expensive, and more efficient, not requiring the transmission of car- 

 riage return and paper feeding signals. 



In addition to the ordinary sending and receiving machines sup- 

 plementary apparatus units may be used so that operators can work at 

 maximum efficiency and the line circuit can be used to its maximum 

 capacity. These units are the perforator, tape transmitter, and 

 reperforator. 



Fig. 5 — Department of Commerce airport teletypewriter station. 



The perforator is associated with a keyboard and perforates a tape 

 with one to five perforations for each key struck. The tape is run 

 through a tape transmitter which automatically sends electrical 

 impulses to the circuit corresponding to the perforations in the tape and 

 identical to those that would have been sent from the keyboard direct 

 had it been connected to the circuit for normal keyboard sending. 

 The use of the perforator and tape transmitter permits the circuit to be 



