airborne navigation and communication systems are disclosed including a vor / loc receiver and a communication transceiver each with separate control and display panels . each panel includes a ten push - button press keys numbered 0 - 9 , a function controller for operating mode selection and general control , a pair of digital displays for displaying keyboard channel selection including an active channel and a standby channel and additional data , three function press keys -- one for switching a standby channel into the active channel or vice versa or resetting the timer or changing the digital bearing display from &# 34 ; to &# 34 ; to &# 34 ; from &# 34 ;, a second key for either recalling a channel or backing up to a digit for correction during data entry , and a third key for storing frequency in memory locations or entering data . the panels are connected to a data processor and the data processor is connected to a plurality of circuits corresponding to the panel functions whereby the panel commands are received by the data processor and the data processor stores the panel &# 39 ; s information in electronically alterable roms , or controls the operation of the plurality of circuits or both in response to the panel commands and generates return signals for display and output to other instruments .