There are cases where what is listed as an "input" frequency is not actually that. One example is the CHP (California Highway Patrol). In their case the dispatcher talks on one frequency (listed as output) and the cars talk on another (listed as input). While cars in some districts are repeated, there are quite a few where they are not. So in my case I must program both frequencies, one to hear each side of a conversation.
There are other situations where knowing an input frequency is very handy. Perhaps you are quite some distance from a repeater, but very close to the scene of an incident. You might actually pick up what is going on more clearly by listening to the input. There's some wild stuff out there and I couldn't describe it all here by any means. Another example might be where an agency changes their CT frequency so the repeater is not triggered. This would usually greatly reduce the area something is broadcast.
GM clam is absolutely right.. The input frequency for my area is the same for both cars and dispatch HOWEVER, once on scene if there is something going on that they do not want dispatch to hear they will broadcast over the air to switch to "Talkaround" or Switch to channel 2 which is the input frequency in the RR for my database, Example, A couple of weeks ago we had a bad lightning storm here, One of the county fire departments repeaters got struck by lightning and it was unusable. .So until it was fixed the switched to channel 2 which was the input frequency on the repeater.. So as GM Clam has stated, The input may be a hassle when something is being toned out etc. because instead of hitting the repeater it may hit the talk around and not be very clear it is also a great assett if something that I have described happens. You'll not hear it very far away I'd say probably a mile or so but IT MIGHT come in handy one day.. I keep my main repeater frequency's programmed in and also my input but I keep the input locked out until something goes on/happens and it's required and then I switch over to it..I have heard some interesting things let me tell you.. Stuff I didn't think would even go on around here.. But you have to be close to hear the on scene talk around, if they're on the other side of the county then don't worry about it because you'll never hear them. I have been there and done that.. But if they're close right under you're nose you will probably hear them.. SO here are some great examples of what the input frequency on the RR could be used for. You can program it in or leave it out, It's your choice, we can't tell you what to do with that but you'll just have to program it in and see what happens. If you never hear anything on it but the samething that you hear on the output frequency then that's probably all it's used for but you just never know and about the only way to find out is program it in and listen awhile and see.. may or may not be used, Never hurts to try/check.. Well I hope between GM and I and also airdorn and pogbobo maybe we've answered your question or questions.. I wish you the best in your finding out about the input and if you have anymore problems or concerns and questions.. Reply here and let us know or start a new thread on RR in the proper forum.. Thanks for being a member of RR, Have a great day!