638 



BELL SYSTEM TECHNICAL JOURNAL 



known as the No. 19 teletypewriter set and is illustrated in Fig. 10. 

 It employs a No. 15 teletypewriter as the page printing unit. 



Fig. 10 — No. 19 teletypewriter set. 



Automatic Retransmission Using Reperforators 



At times it is desirable to retransmit messages received from one 

 circuit to some other machine or machines on a separate circuit. A 

 unit known as a "reperforator" is often used to facilitate such re- 

 transmission. The reperforator now standard for the Bell System is a 

 start-stop receiving device using the 5-unit permutation code. It is 

 somewhat similar to the receiving-only tape teletypewriter except 

 that the record produced consists of code perforations in a tape rather 



