What is a standard two call system?

Thanks!

She gives you better directions.  You call when you are close, she tells you the room number.

Swim

I don't really get what purpose that serves .....

When I did incall, I had this system. they called for the appt, we set up a time and day. WHen close, with in 5 mins, they call again. This serves many purposes, if hes a no show you know it before hand. If another client was running over, I would come up with an excuse for him to wait. No knocking at the door at the wrong moment. And no clients ever saw eachother, plus I couldn't always rely on the doorman to make sure he was annouced, and I never wanted a client sitting in the lobby just in case.

Now that I do outcall, which I find so much easier, I do the 2 call system different. FIrst call is made with the appt. Second call when I am a block away from their destination. This is good, because most time business men are on the phone or are on same trip with co-workers in different rooms. You never know what you could walk into.

Once I arrived, confirmed with the second call a block away, got to hotel room, knocked, he opened door enough for me to see he was not alone, anhd I just said, o I'm so sorry, wrong room. Hi co-worker was like. Please stay..I laughed it off and said thanks but no thanks. His co-worker had no clue who or why I was there.

CLient called me 5 mins later and said how sorry he was, and I came back, and he paid me double just because I handled the situation so well.

Usually the lady will give you a location near where she is.  It might even be the hotel, but not the room.
Stuff happens.
You call when you arrive at the call point, no more than a couple of minutes before the appointed time & she gives you the final approach.  
Why?  Often a lady can see the call point.  I once called from the wrong hotel door & the lady said "I can't see you?  Where are you."  I told her & everything went fine.  
She may have reservations but not a room number when she makes the appointment.  
It makes it more difficult for stalkers or LE  showing up unannounced.  
skb

Depends on where you're working.  If you are working out of your home, it limits who has your address to actual clients as opposed to NC/NSes.