WIRE COMMUNICATION AIDS TO AIR TRANSPORTATION 469 



airways, principal airports, and cities are shown on tlie map and in the 

 upper left corner is a small circle used as a coordinating point. 



At a scheduled time the operator at Kansas City or Cleveland inserts 

 in a teletypewriter equipped for perforating tape a copy of the map 

 on which the latest weather information has already been typed 

 including general state of weather, ceiling height, visibility, tempera- 

 ture, wind direction and velocity and barometric pressure for each 

 point and isobars connecting points of equal pressure. The sending 

 operator then types the identical symbols, letters, and figures directly 

 over the corresponding ones on the map inserted in his machine, 

 thus making a complete record on perforated tape. On schedule a 

 blank map is inserted in the teletypewriter at each receiving point and 

 positioned so that a type bar will strike the map within the small 

 coordinating circle. The sending operator then releases the tape and 

 the signals transmitted over the circuit reproduce on the map at the 

 receiving stations data similar to those on the original map at the 

 sending station. 



The map data are sent in sequence from the two transmitting stations 

 and after they have been received on the map forms a number of 

 duplicate copies can be run ofif immediately and the two maps fitted 

 together if desired. The maps are then available to pilots at each of 

 the respective airports. 



Complete reports of weather are generally maintained by transport 

 companies in dispatching offices. On some lines two-way short-wave 

 radio telephone equipment has been provided for communicating with 

 planes and periodic contact is maintained during flight. In this way 

 pilots report their positions directly to dispatchers and in addition 

 supplementary weather data are usually exchanged, particularly in 

 respect to local ceiling heights and conditions in the upper air strata. 



Plane Dispatching and Other Service 

 Teletypewriter circuits furnished to air transport companies are used 

 principally for dispatching planes and handling the many traffic 

 matters usual to this type of service. Plane movements including 

 reports of position in flight are transmitted over the teletypewriter 

 system and recorded at various offices. The reports of positions, in 

 many cases, are given by pilots over short-wave radio telephone where 

 this type of equipment has been provided. 



To facilitate position reporting some of the companies have super- 

 imposed a system of rectangular coordinates over a map of the course 

 cutting the territory into squares or rectangles 10 to 20 miles on a side. 

 The coordinates are numbered so that the pilots and dispatchers can 



