7K • Chapter 7
7-50
Phone Line Control Mode
Phone Line Busy Input
The Phone Line Busy Input is used to inform the controller that the phone line
is being used by another device, and that it should not access the line. This
input is normally held high by a pullup resistor. When this input is pulled down
to ground by an external device, it is asserted active.
If a “line relay” is connected to a standard telephone, its contacts can “busy-
out” the controller when the telephone is picked up.
The controller will ignore ringing on the phone line when the phone line busy
input is active. This feature is necessary, since the controller may be sharing
the phone line with a rotary phone. The rotary phone, when dialed, creates
interruptions in the phone line voltage which appear as ringing signals to the
controller. Such activity could cause the controller to go off-hook.
Phone Line Busy Output
The controller activates the Phone Line Busy Output during autopatches and
phone line control sessions to inform other devices at the repeater site that the
phone line is in use.
The Phone Line Busy Output is an open-drain power MOSFET device and may
be used the same way as logic outputs.
If several controllers are sharing the same phone line, connect all of the Phone
Line Busy Inputs and Phone Line Busy Outputs together. The first controller to
access the phone line will “busy-out” the remaining controllers.
Phone Line Answer Modes
Mode programs the controller for the way you want it to operate when it
receives incoming ringing signals from the phone company. Mode is single digit
0 to 4.
Mode 0
This is the Do Not Answer Mode.
Mode 1
After a delay of 00–99 incoming rings, begin ringout for reverse patch at a rate
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