[comp.sys.mac.hardware] Interfacing a phone - need small schematic

jjoshua@topaz.rutgers.edu (Jon Joshua) (04/12/90)

I am building a hardware/software project for the MAC and I need some
help with the hardware part.

I need a small interface that hooks into a phone line and the Mac's
RS422 serial port.  When a phone is off-hook the interface should
raise the signal on the handshake line.  When the phone goes back
on-hook the interface should clear the signal.

From what I understand RS422 uses -1 and +1 and not 0 and 1 values.
Is this correct?


Thanks for any help.


JOn.
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