Baron 58 Cockpit Simulator

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KT70 Mode S Transponder

Panel design 

Components and PCB

PCB, using the opencockpits 7-segment display holders in my own PCB.

PCB with the opencockpit 7-segment display holders

Transparency sheet that will cover the 7-segment display and the leds

Components (roughly) in place


PCB Design (draft)

Print of design and components

Functions of the KT 70

Real KT70

Picture of Real KT70

Restyled and equipped with enhanced backlighting and controls, the Bendix/King Silver Crown Plus KT 70 Mode S transponder also offers Mode A and Mode C compatibility. Identical in appearance, the Silver Crown Plus KT 71 Mode A/C transponder is a cost-effective alternative.


IDENT BUTTON – Marked IDT, the KT 70/71’s Ident button is pressed when ATC requests an “Ident” or “Squawk Ident” from your aircraft. 

ID CODE – The ATCRBS Transponder Identification code (squawk code) for the aircraft is displayed inthe Ident Window on the right side of the display. Each of the four Transponder Code Selector Knobs selects a separate digit of the identification code.

REPLY– The lighted “R” reply indicator blinks when the transponder is replying to a valid interrogation.

ALTITUDE DISPLAY– The KT 70 and KT 71 display Flight Level Altitude, marked by the letters “FL” and a number in hundreds of feet.

VFR – The VFR Pushbutton recalls the preprogrammed VFR code, superseding whatever code was previously entered.

FUNCTION SELECTOR KNOB – The Function Selector Knob enables you to choose from among the following operating modes:

OFF– The unit is not receiving power.

SBY (STANDBY) – In Standby, the KT 70 and KT 71 are energized but are inhibited from replying to any interrogation.

TST (TEST) – Replies are disabled in test mode, and the unit illuminates all segments of the display for at least four seconds. A series of internal tests is performed to check the KT 70/71’s integrity, verifying all EEPROM data and making hardware and squitter checks.

GND (GROUND) – In the KT 71, all interrogations are inhibited. In the KT 70, Mode A & C interrogations are inhibited, but the KT 70 will reply to all valid Mode S interrogations. An optional remote “air/ground” switch may be installed on the aircraft’s landing gear strut to keep the KT 70 and KT 71 in the GND mode until the airplane is airborne.

ON– The KT 70 is able to reply to all valid Mode A, C and S interrogations (Mode A and C on the KT 71); however, altitude information is suppressed.

ALT – In the “ALTITUDE” mode, the KT 70 replies to all valid Mode A, C and S interrogations (Mode A and C on the KT 71).





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