jpp412

I haven't even connected any load to it yet - the regulators are cool.

Hey Audio, Yes it is about 18v according to the DVM.

I don't think that's the problem - at least based on what I had ordered the 7812 was from TI and I used the pinout on their datasheet. However is there someway I could check it? - short of removing it from the circuit and using separate test circuits?

CHeck out the post on "electronics chit-chat" forum for a pretty good list.

I have a problem with a 7812 in a power supply such that the output voltage (measured with a dvm) is only 9.5v. I at first thought the 7812 was bad so I put a new one in and still getting the same results. I have a 7805 and 7905 in the same supply that work fine. Any thoughts? Is is possible that I got a batch of 7812's that are no good? (or perhaps mismarked 7810's) Thanks in advance. Joe

Thanks Audioguru. Your explanation helped alot. I'm going back through their ex apps with this in mind to see if I can make sense of it now. Thanks again! Joe

I'm trying to understand the function of the 339. I have read all of the datasheets (which don't help very much as far as basic understanding) and think that the basic idea is to output high when the + input is > the - input and a low otherwise. Is this the correct basic idea? Beyond that - when I look at the example datasheets which include application examples - I find that most of the examples elude me in terms of what they will do. Any help or pointers to resources that I could study would be much appreciated. Thanks in advance. Joe

You can just buy the digital pot - check out digikey.

Sorry about that. Here is the link: http://www.electronics-lab.com/projects/telephone/017/index.html

I'm trying to figure out the microcontroller program.

Has anyone built this circuit that could help with my questions? Also, I noticed another circuit ("8-line telephone intercom") posted by someone else - is that a better design for me to try instead of the link 4+0?

Hey Austin et al: I am new to this forum and am interested in building the link4+0 for personal use. 1. However, I am somewhat new/inexperienced with this type of thing. I don't see any identification of the parts required to build. Most of them I can figure out by looking at the previous design but not all of them. 2. Why can't this be used for up to 8 phones? Any help would be appreciated! Thanks, Joe

Hey Austin et al: I am new to this forum and am interested in building the link4+0 for personal use. However, I am somewhat new/inexperienced with this type of thing. I don't see any identification of the parts required to build. Most of them I can figure out by looking at the previous design but not all of them. Any help would be appreciated! Thanks, Joe