Specifications

AN93
Rev. 0.8 149
sent initially).
If an OK (dial tone present) was received after the
ATDTW;<cr>, the line requires pulse dialing. Pulse dial
the entire telephone number using ATDP12345<cr>.
Method #3: Adaptive dialing
Adaptive dialing attempts to dial with DTMF, then falls
back to pulse dialing. It is enabled with bit 6 of U7A. If bit
6 is set, the first digit is dialed with DTMF, and the
Si2493/57/34/15/04 waits 2 seconds. If a dial tone is still
present, the first digit is resent with pulse dialing
followed by the other digits in the dial string. If dialtone
is not present, the remaining digits are dialed with
DTMF. Adaptive dialing does not select 10 pps vs.
20 pps dialing. This must be configured beforehand.
This method always results in pulse dialing when used
with a PBX since a dialtone is sent after the first
number.
Automatic Phone Line Configuration
Detection
The modem may automatically determine the following
characteristics of the telephone line:
DTMF or pulse dialing only
 Determine if 20 pps is supported on a pulse dial only
line,
 Identify it as an outside line or extension network
(PBX)
 If connected to a PBX, determine if the dial tone is
constant or make-break
 If connected to a PBX, determine the number to dial
for an outside line
The AT&X1 command automatically determines the
above parameters through a series of off-hooks and
dialed digits.
Line Type Determination
The digit dialed to determine 10 pps vs. 20 pps is
programmable through S51. The &X2 command works
as described above; however, only DTMF/20 pps/
10 pps determination is made (no PBX). The &X1 and
&X2 commands may be aborted by sending the
command, AT&X0. The result code will be “OK.”
Telephone Voting Mode
The telephone voting mode (TVM) of operation monitors
the line to detect polarity reversals after dialing. It waits
for a busy tone to be detected and reports “POLARITY
REVERSAL” or “NO POLARITY REVERSAL” followed
by “OK”.
To enable TVM, use the “G” character in the dial string
(eg. ATDTG1). The “G” character must be used for each
TVM call. The S7 timer operates during TVM and
indicates “NO CARRIER” if a timeout occurs before the
busy tone is detected. Polarity reversal monitoring
begins after the last digit is dialed and ends at the
detection of the busy tone. Any loss of line-side power
(drop out) is considered a polarity reversal if loop
current is restored within U51 milliseconds.
Table 99. Automatic Phone Line Configuration
AT
Command
Result Code
&X1
WXYZn
W = 0 line supports DTMF dialing
1 line is pulse dial only
X = 0 line supports 20 pps dialing
1 line supports 10 pps dialing only
Y = 0 extension network (PBX)
1 connected to outside line
Z = 0 continuous dialtone
1 make-break dialtone
n = 0–9, number for outside line