While reporting arrival and departure, sometimes called "O-S-ing" in later TT&TO eras, was done by the prototype Aquia Line, it is really not necessary on the model railroad, as the dispatcher doesn't have much else to do. The main purpose of this system will be to allow the dispatcher to maintain a train sheet and to create a realistic noise. The telegraph is in effect adding "audio scenery" to the layout.
Where to put the dispatcher? Probably the best place is in the home office area. Since the dispatcher will usually be me, and I need to go in and out of the office during an op session to answer questions, fix problems etc, I don't want to be trapped in the office with a duck under section of layout in the way. So if I went with layout design v19 I would need to make a gate or other section to allow access to the office.
Or, I could change the design and go to a version 20 see below. This version adds a passing siding at Potomac Creek by moving Stonemans and Falmouth into the main room, thus making 5 possible places for meets. The extra passing siding is not that critical as the train density would not change, but the extra length of run wouldn't hurt.
The blob by Robert's Ridge would make it impossible to have a couch in that part of the room. To compensate, I would move the crew lounge to the office area. But then I couldn't have too many book shelves in the office. I could install book shelves under Falmouth and Roberts Ridge to make up fo r the loss in the office. The aisle by Falmouth could be a problem especially with two train crews there, so I made the aisle in that area as big as possible. In this design, I lose the expanded Burnside's wharf, in return for a longer run and easier access to the office. However, it does keep open a possible expansion of Burnside's Wharf into the office if I run out of things to do later too.
All this just to hear some noise ripple across the layout.