Can't hear when the call is on speaker.

Put it on concrete and hit is with a large hammer. The will disable it.

Lifting the handset will disable the headset for that call. Recorder mode records your call.

Comdial Digitech DSU Impact Telephones User's Guide

Is is call 'Night Transferred'. This says it is done with a button. The manuals are dreadful! I can't find anything 'timed'.

https://www.manualslib.com/manual/186263/Comdial-Dsu-And-Dsu-Ii.html?page=34

https://www.google.com/search?q=comdial+impact+system%2C+change+night+transfer+time

https://www.manualslib.com/products/Comdial-Impact-8024s-Series-414094.html

..

It means there's "No Such Station" :-)

VM extensions are part of the system, usually the pilot number is the lowest of the sequence. If your button got reprogrammed and you're dialing a number that doesn't exist, you'll get that error.
Start by dialing like 22, 23, 24, 25 (4 highest ports in a 0816 DSU). Reprogram the button by Intercom **1 press the button and dial 6xx where xx is the VM pilot number.

Carl

Sure. #4 picks up the extension if it's ringing in your group, *4 + ext is directed. It's in a manual on page 18 http://www.wedophones.com/Manuals/comdial/DSU%20and%20DSU%20II/DSU%20II%20Non%20LCD%20Speakerphone.pdf

Carl

hit the options jey till you get to dss then press the button you want to program and then enter the exstension number you want it to be and then when finished press speaker button

it could the prot is programed for the wrong phone type or the [port could be bad you can contact me at [email protected] depending on what area you are in i can help you or recommend a dealer in that area

send me a email at [email protected] and i will email you instructions

Restart your phone system. Let it stay off for a minute.
If problem continues look what is connected to your music on hold port. Look into that media device and conection methods. If nothing connected you will need to contact your local Comdial Vendor.
Cheers

press ICM button
Dial # 1
hould shut off light its the background music feture
and you must not have music on your system

Press ITCM # 1 to turn off Speaker button light