WIRE COMMUNICATION AIDS TO AIR TRANSPORTATION 475 



A separate reperforator (A) and tape transmitter (B) m addition to 

 a tape teletypewriter (C) are provided for each circuit. Messages are 

 received simultaneously on a printed tape by the tape teletypewriter 

 and on a perforated tape by the reperforator. Mounted adjacent to 

 the reperforators are the tape transmitters through which the per- 

 forated tape can be run to retransmit immediately a received message 

 to another circuit. The reperforators and tape transmitters can be 

 started and stopped individually from the remote control box (H). 



A tape perforator (K) is provided to perforate tape for messages 

 originating at the local station. The messages can then be sent 

 automatically over the circuit or circuits desired by running the tape 

 through the proper tape transmitters. 



All of these units are terminated on cords and plugs at a loop switch- 

 board (£) and any unit or combination of units may be connected to 

 any of the teletypewriter circuits which are wired through a number 

 of series jacks in the loop switchboard. A supplementary switching 

 arrangement is provided by radial transmitting board (G) equipped 

 with keys and repeating relays. By operating one or more of the keys 

 one of the tape transmitters can be connected quickly to two or more 

 of the teletypewriter circuits through the repeating relays to obtain 

 simultaneous transmission to the circuits connected. 



At certain stations page teletypewriters {D) are provided for the 

 transmission of weather maps as described previously. This type of 

 machine employs a fixed paper carriage and movable type basket, and 

 accommodates paper up to 8)4 inches wide. It has been equipped with 

 a number of special type characters to provide the symbols required on 

 the maps. These symbols, which are shown in Fig. 3, are provided as 

 upper case characters on the teletypewriters in place of fractions and 

 punctuation marks. 



The arrangement of equipment described generally permits one 

 operator to attend all of the circuits. The teletypewriters are all 

 located in a fairly small space, which permits one man to observe the 

 incoming messages and operate the control boards, to start and stop 

 the proper transmitter and to relay the messages as required. 



Radio Interference 



The establishment of teletypewriter stations along the airways 

 brought about the installation of teletypewriter equipment in the 

 same room or in close proximity to short-wave radio receivers, and 

 introduced the problem in specific cases of radio interference caused 

 by the operation of the teletypewriter. 



Remedial measures have been designed effectively to reduce this 



