This is where you need to re-program your thinking as to the meaning of "lines". Your description relates to how multi-line phones operated in the past. Each telephone "line" was wired to a button ("a key") on the phones. So, you could have 4 lines coming into 4 phones, with each line represented by a button on each phone. As Ross said, this is called "key system". While this old technology made it somewhat simple to manage a small system, it doesn't scale very well. Also, if User A wanted to phone User B, he/she had to dial the "outside phone number" to come back in on another "line". Unless User B was in a completely separate part of the building, this never works very well, as the incoming call just arrives as another call, not to a specific User. Someone would answer "the call", and probably would have to Page the User in the other part of the building. Not too convenient.
With a PBX, the "lines" are called "trunks", as they terminate at the PBX. The PBX sits between the trunks and the telephone extensions. In this manner, each extension is completely independent, and can make internal calls simply by dialing it's extension number. The call never leaves the building, and is directed to the desired party. The PBX takes over the chore of monitoring the trunks, so these functions never need to be presented to each extension.
The "Hold" feature has been replaced by the "Park" function. A little mind adjustment is required in using it, but you can have as many "Park slots" as you wish. It is also possible to configure "multiple extension" IP phones with a "Busy Lamp" indication of Parked Calls, or your buddies extension. Some phones are easier to configure than others.
While my babble doesn't fix your problem directly, it is critical to nudge your thinking along the lines (oops, bad term) of how the technology functions.
Good luck. Hope this helps.
Hey thanks for the clarification!
In this case, yeah what I meant is the trunk used to be shown in all phones.
I did some parking lots tests yesterday, but I have some issues.
What is the difference between blind parking and blind transfert (phone softkey button). Isn't blind transfert and putting "70" because blind parking? The thing is I was able to park that somewhere, and repick it up to another phone by pressing *85. But the problem is that used trunk (caller waiting), will keep waiting forever if we forget that we have a blind parking since there is no indication that a trunk is used.. The other problem is this example:
Phone A receives a call want want to transfer to Phone B.
When Phone B isn't busy, it is ok. Phone A needs to press transfer to extension of Phone B by pressing the "transfer button on the phone" and then follow by extention of phone B. No problem here.
Problem is when phone B isn't free, Phone A will not be able to transfer to B, because after a number of rings, it will terminate the call (because Phone A will not see the trunk anymore, while it will timeout while waiting for phone B to answer). The only solution I had found was to Phone A to transfer to a Queue, which is a queue for Phone B... The other solution is Phone A puts on hold the call, until Phone B is free, and transfer it to Phone B --> however the problem is it requires someone to be beside of Phone A to make it possible, which in the business of a Pharmacy for example, isn't working well, because staffs needs to do other stuffs than waiting in front of the phone..
I have difficulty to understand call transfer and call parking, is it the same, while the only difference is 70 = parking slots and 101 extension = transfer?
And also, is the hold button on the phone same as call parking? In this case, which slot is it? Because I can't really pick it up from another phone...
Lastly, this (It is also possible to configure "multiple extension" IP phones with a "Busy Lamp" indication of Parked Calls, or your buddies extension. Some phones are easier to configure than others.) sounds cool. Would like to read some info about it.