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C00002 00002	Vadic dialer/modem protocol
C00005 ENDMK
Vadic dialer/modem protocol

To initiate a call on the Vadic dialer the following sequence of characters
should be sent to the modem:

1.  STX ("α", octal 002).  This starts the transaction.

2.  Dialing digits, ascii 0-9.  If "=" (octal 075) is sent, the dialer will
wait for another dial-tone before proceeding.  If "<" (octal 074) is sent,
the dialer will stop dialing at that point and transfer to the modem whether
the other end answers or not (don't do this).  Up to 31 digits may be given.

3.  S1 ("∂", octal 017).  This indicates end of buffer.

4.  ETS ("β", octal 003).  This actually starts the dialing from the buffer
just sent.

At this point, the dialer will respond with a single character.  The meanings
of each are as follows:

"A"  Call completed with no problem, a data set answered and control is transferred
to the modem.  To hang up, the modem's <break> protocol must be invoked.

"B"  Call did not go through.  This is caused by Trunk Busy, Remote Busy, and
Ring no answer.  Also a resoponse to an abort (see below).

"G"  Data line occupied.  dialer's phone line is busy.

Other good things.

If the dialer doesn't like the character you just sent it, it will respond as

"D"  Format error

"E"  Parity error

"F"  Too many digits in number.

At any time before the receipt of an "A", you can send the dialer a SOH character
("↓", octal 001) to abort.  The dialer responds with "B".  If a number has been
sent to the dialer it is remembered and can be redialed.  This is usually done
when the dialer reports that the call did not go through.

If a complete phone number has been sent to the dialer, the same number can be
redialed by sending STX and then ETX.  This can be done after a complete call,
or after the call has been aborted.