Apollo SL70 Operation Manual

Using Altitude Hold

Altitude Hold helps you maintain a constant altitude. The current pressure
altitude is stored as a reference and is the displayed value u nless Altitude Hold
is activated. The hold altitude is displayed in 100-foot increments. The
displayed altitude is the same as is sent for Mode C interrogation replies.
When the HLD button is pressed, the altitude display will be set to “+000.”
The altitude display values will increase/decrease as the aircraft changes
altitude. The altitude display will flash when the aircraft change in altitude
exceeds the selected threshold.

Setting the Hold Altitude

1. Press the HLD button to set the current altitude as the hold altitude. The

LED above the HLD button will light to indicate Altitude Hold is active.

2. The Altitude display now shows a value that is relative to the hold altitude

in 100-foot increments. A displayed value of +001 means you are 100 ft
above the hold altitude.

Setting the Altitude Hold Buffer

1. Set the Altitude Hold Buffer value by pressing the HLD button for two

seconds, or longer. Select a value between 200 and 2500 feet. The factory
default value is 300 feet. The value is retained when the SL70 is turned off.

2. Turn the S

MALL knob to change the buffer value, such as ±02. Press HLD

again to save the value.

Displays

Squawk Codes

The four-digit squawk code is shown on the left side of the display.

Altitude

The Altitude display is used to show the pressure altitude, Hold Altitude, and
Hold Altitude buffer with 100 ft resolution.

© 1999 by UPS Aviation Technologies, Inc. All rights reserved. Printed in the

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Apollo

®

Mode C Transponder

Model SL70

Operation Manual

August 1999 560-0401-00

Apollo SL70

The Apollo SL70 Mode C Transponder complements the Apollo SL series of
slimline avionics. The SL70 provides Mode A/C functionality certified to
TSO-C74c Class 2A meeting VFR and IFR requirements, operates on 10-35
VDC, includes squawk code display and selection, standb y, altitude, and ident
operation. All of these features are contained in the space-saving 1.3”H x

6.25”W form factor, with bright easy-to-read LED characters, and user­friendly operation. A photocell on the front of the SL70 adjusts the LED
intensity for ambient light conditions. The SL70 will automatically test its
receive function if no interrogations have been received in the last 30 seconds.

Knobs

A single knob on the left side controls power on/off. Rotate the knob
clockwise to turn transponder power on. Rotate the knob counterclockwise to
turn power off.

Dual concentric knobs on the right side are used to select squawk codes and
change altitude values. Turning the large, outer knob moves the cursor to
allow editing of the selected character. Turning the small, inner knob changes
values.

Pushbuttons

Press the pushbutton once to activate the selected operation. An LED above
each pushbutton will light when that button is pressed.

IDENT

Press the IDENT button once to reply with an identifying squawk code, Ident
mode. In Ident mode, the Reply LED will be lighted for 20 seconds. The
Reply (Ident) LED will also flash when the SL70 generates transponder
replies.

SBY

Press SBY to place the transponder in “Standby” mode. The SL70 is “on,” but
no information will be transmitted.

ON

Press for Mode A operation. The SL70 is “on” and will transmit its squawk
code when interrogated.

ALT

Press for Mode C operation. The SL70 is “on” and will tra nsmit its squawk
code and altitude when interrogated.

VFR

Press VFR once to set the VFR squawk code. Press VFR a second time to
toggle between the VFR squawk code and the previously entered code.

HLD

Press to enable/disable altitude hold. The LED above the HLD button is
lighted when altitude hold is enabled.

Selecting a Squawk Code

The selected squawk code will always be in use. As you change a squawk
code, the original code will be sent until you are finished selecting the ne w
code. When changing a code, the display will stop flashing and selection is
stopped if the controls are not used for three seconds or more. Pressing any
pushbutton will also end code selection. The squawk code is automatically
reset to the VFR code when the SL70 is turned back on.

1. Rotate the

LARGE knob clockwise one position. The first character of the

squawk code will flash.

2. Rotate the

SMALL knob to the desired number for the first digit.

3. Rotate the

LARGE knob to move the cursor to the next desired digit. Turn

the

SMALL knob to select the desired number.

4. Repeat step 3 for each of the desired digits.