FUNDAMENTALS OF TELETYPEWRITERS 635 



The tapes employed may be either gummed on the back for con- 

 venient pasting on blanks for filing or may be plain paper tapes if the 

 records are of temporary interest only. Also cellophane or similar 

 transparent tape may be used if it is desired to project the record on a 

 screen. A tape out signal is provided on the machine so that when a 

 roll of tape becomes nearly exhausted a bell will ring continuously to 

 give warning of this fact. Where a bell is not desired, the last few feet 

 of tape on the roll are painted red to give similar warning. 



If desired, this tape printing machine may be used on the same 

 circuit with page printing machines such as the No. 15 teletypewriter, 

 and when so employed is usually equipped with an "end of line 

 indicator" to warn the operator of the approach of the end of the line 

 in the page machine, so that suitable signals may be sent for starting 

 a new line. 



Features of TWX Switchboard Operators' Teletypewriters 



Such machines must be small in size to permit their use in a switch- 

 board position, quiet in operation to permit their use in the same room 

 with a telephone switchboard and must be capable of working with 

 any machine employed in the TWX system. 



To meet these requirements the standard No. 14 tape teletypewriter 

 has been modified in several important respects as follows: 



1. It has been provided with a specially designed enclosing cover 

 which reduces the machine noise radiated by at least 5 db more than 

 standard covers. 



2. The machine is tilted so as to raise the keyboard and permit the 

 operator to assume a more elevated position nearer the switchboard 

 jack field. 



3. It is equippent with an end of line indicator mechanism and lamp 

 to warn of the approach of the end of a line when sending to a page 

 teletypewriter station so that the proper signals may be sent to start 

 a new line. 



4. The usual tape feeding mechanism which pulls the tape past the 

 typing point and obscures some of the typed message is replaced by a 

 so-called "push feed" mechanism which acts ahead of the typing point 

 and makes the typed message more fully visible. 



5. Many of the operators' machines are provided with specially 

 arranged power supply and governing circuits so that their motors 

 normally run from 115 volt a-c. commercial supply but in case of a 

 power failure can be quickly switched to run from the 130 volt d-c. 

 telegraph battery. 



