Safe lock help · Protex
Safe lock troubleshooting › Protex › Protex electronic drop box (SDL-400E and the 9V-contact keypad)
Protex electronic drop boxes (like the SDL-400E) use a DigiPaz keypad with a green “open” light, an orange “alarm” light and a red “low volt” light. They have a user code (4 to 10 digits) and a second master code. Protex also has a drop box manual for a keypad with two columns of keys and two battery contacts under it. This guide covers how to open the box, change the codes, replace the batteries, and use the override when they are dead.
Want the whole manual? Jump to the manufacturer download links.
Is this your lock?
- SDL-400E (and similar): a keypad with the digits, a * key and a # key, three lights (Alarm orange, Low volt red, Open green) and a turn knob below it. Its Protex manual is V 10.4.12.
- It uses four AA batteries in a battery box in the back of the door, and a black external battery box for emergencies. The outlet is on the top right edge of the keypad.
- The other Protex drop box manual is for a slim keypad in two columns (1 to 5 and 6 to 0, then * and #) with a light above it and two metal battery contacts under it.
How to open it
- Enter your user code and press #. (On the other drop box, press * first, then the code, then #.)
- The green “open” light comes on and you hear a beep.
- Turn the knob clockwise and open the door. You have 3 seconds on the SDL-400E (5 seconds on the other drop box). Then the box relocks itself.
- To lock, shut the door and check that it is locked.
- A wrong code makes the orange “alarm” light flash with 3 rapid beeps. Try again.
- Always press # after the last digit.
How to change the battery
The SDL-400E uses four AA alkaline batteries (we recommend Procell) in a battery box in the back of the door. When the red “low volt” light comes on, change them. The safe keeps the code in memory for up to 6 months without power, so you do not need to reprogram it after changing batteries. Never use old or leaking batteries.
- Find the battery box in the back of the door.
- Remove the screw and the battery cover.
- Take out the 4 batteries and put in 4 new alkaline AA batteries.
- Replace the cover and check your code.
Dead batteries: the battery override box (SDL-400E)
- Put 4 AA batteries in the black external battery box that came with the safe.
- Find the outlet on the top right edge of the keypad and plug in the jack.
- While the box is plugged in, enter your code as usual and open the safe.
- Replace the batteries inside the safe, then unplug the override.
Dead batteries: the other Protex drop box
- Hold a 9-volt battery against the 2 battery contacts below the keypad.
- Enter your code while the battery is held to the contacts.
- Replace the batteries in the back of the door.
- The override is only for an emergency. Never lock the override battery box inside the safe.
How to change the codes
Do this with the door OPEN.
Check your new code at least 3 times with the door open before you close the box. The starting codes are in Protex’s manual and with the box paperwork. We are not printing them here. Write the new code down only while you set it, then destroy the paper. Never lock your code inside the box.
SDL-400E: user code (4 to 10 digits)
- Open the door and turn the knob so the bolts are out (the locked position).
- Press # 2 times. This puts the lock in code-change mode and the orange LED lights.
- Enter your existing code (the factory code if you never changed it) and press #.
- Enter your new 4 to 10 digit code and press #. The green “open” LED lights and two beeps confirm the new code.
- Check it: enter the new code and #.
SDL-400E: master code (6 to 10 digits)
- Press and hold # for 5 seconds until the orange “alarm” LED blinks.
- Enter the existing master code and press #. The green “open” LED stays lit.
- Enter a new 6 to 10 digit master code and press #. The green LED lights and you hear 2 fast beeps.
- Try the new master code, followed by #, to open the safe.
The other Protex drop box (code 1 to 9 digits)
- Open the door and leave it open.
- Press * then #.
- Press *, then your existing code and #.
- Enter your new code and #, then the new code again and #. Your new code is set.
- Try it with the door still open: *, the new code and #.
- Do not pause more than 7 seconds between steps on the SDL-400E change.
- The master code works as an extra code. Protex says to remember it, because it is your way in if the user code is lost or forgotten. If you open the box with the master code, the user code returns to the factory setting, so set it again.
Lights and beeps
| What you see and hear | What it means |
|---|---|
| Green “open” LED and a beep | A good code. Turn the knob now. |
| Orange “alarm” LED and 3 rapid beeps | A wrong code. |
| Orange LED on and the keypad will not respond | The lock is in lockout after 3 wrong codes. |
| Red “low volt” LED | The batteries are low. Change them. |
| Green light on but the box will not open | The batteries are low. Replace them. |
| Orange LED on (code-change mode) | The lock is waiting for you to enter the code. |
| Indicator blinks and 8 beeps (other drop box) | The battery voltage is low. |
Wrong-code lockout
SDL-400E: three wrong codes in a row put the lock into lockout and there is no response from the keypad. Page 2 of Protex’s manual says wait 5 minutes, and its troubleshooting table says wait 12 minutes, so wait the longer time. Other Protex drop box: four wrong codes in a row sound an alarm for 20 seconds.
If it still won’t open
The keypad does not respond
The batteries are probably dead. Use the override battery box (4 AA, plugged into the top right of the keypad) or the 9-volt contacts on the other drop box, open the box, then change the batteries inside.
I forgot the user code
If you set a master code, it will open the box (and puts the user code back to the factory setting). Otherwise please do not keep guessing: call us.
The green light is on but the box will not open
The batteries are low. Replace them.
Download the full manufacturer instructions
This page is a quick-reference summary. For every feature and diagram, use the official manual for your model:
- Protex SDL-400E Programming and Operation manual (PDF, V 10.4.12)A Protex Safe Co. manual, from Protex’s Manual page.
- Protex Drop Box User Manual (PDF)A Protex Safe Co. manual, from Protex’s Manual page.
- Protex Safe: Manual pageProtex’s own page of user manuals.
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More lock guides
About this guide. This is an independent guide from Steve’s Lock, Safe and Alarm, a safe and lock dealer. Brand and model names belong to their owners and are used only to help you identify your lock. We are not affiliated with the manufacturers. These steps summarize the manufacturers’ own instructions; your lock may be a different version, so if anything here does not match what your lock does, follow your manual or call us. Always change codes with the safe door open, and test the new code several times before you close the door.
Steps last checked against the manufacturer documents on October 19, 2026.