Won't happen. The call would be dropped. AFAIK, a change from "home"
> to "roam" means you are changing carriers. Calls in progress are NOT
> passed or handed-off from one company to another. (It appears that
> they usually can't even pass from one tower to another within a
> company.)
In earlier days of cell phones, I don't think it was so much going to another carrier, but rather going out of your personal defined service territory with your calling plan. In other words, it wasn't a technical or physical boundary, but an adminstrative or billing one.
For instance, I have Verizon (nee Bell Atlantic-Nynex). Even under Bell Atlantic there was a huge service territory of several states, but phones were limited to a specific metropolitan area. Size of that area varied by your calling plan (as did the cost of roaming). So, in most cases it wasn't a matter of leaving your carrier, but rather leaving your home area. They had some $15/month plans that were limited to about a single county.
Since roaming for me was so expensive, I was careful not to roam, so I don't know how the plan handled split calls. If I attempted a call on roaming, a yellow light would blink on my phone.
I found that near the border of my roaming area I have to be careful. For example, at a particular rest stop on the turnpike, sometimes I'll roam (and pay) and sometimes not. This is because even from a fixed physical spot, multiple antennas in different places could handle your call. Even on calls from my front stoop the bill shows three different antennas at different times.
Obviously a disadvantage of my cheap plan ($19.95/mon) is limited roaming and expensive fees ($1/min) if I do. Today's $40/mon plans have much bigger roaming areas, but you're paying for that in the monthly fee. For an occassional user like myself, my plan works best for me and I'll pay the $1/min in the very rare times I have to.
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