TECHNICAL BULLETIN #184 - Rev 1.00 (8/1/96)

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TITLE   : Setting Up Silent Answer
PRODUCT : PROCOMM PLUS 3.x and 2.x for Windows
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Silent Answer is a modem technology that allows a modem to distinguish between 
different types of incoming calls. Silent Answer is similar to Adaptive
Answer, but instead of determining if a call is data or fax, Silent Answer
determines if a call is voice or fax. Silent Answer Plus will discriminate
between voice, fax, or data. Silent Answer is currently an exclusive
technology of Supra Corporation's SupraFAXmodemsTM.

Silent Answer operates in the following manner:

 1. A call comes in.

 2. On the first ring signal, the modem partially picks up the line and
    listens (snoops) for fax CNG tones. On some external models, the OH light
    may turn on. This snoop cycle will last 2-3 seconds.

 3. If no CNG tone is heard, the modem will hang up so it does not interfere
    with the next ring signal.

 4. If a person or answering machine answers, the modem will again snoop for a
    CNG tone for 2-3 seconds. It will again hang up if no CNG tone is heard.
    Because the CNG tones cycle is 4-5 seconds, these 2-3 second snoop cycles
    may not detect the tone.

 5. If the modem does not receive another ring, or if no CNG tone is heard 6
    seconds after the last ring, a 6 second snoop session is started.

 6. If CNG tones are detected, the modem will answer as a fax. When the modem
    answers, several RING's will be sent to the terminal screen so that the
    software will answer.

 7. If Silent Answer Plus is in use, the modem will also listen for a calling
    tone (1300 Hz for 600ms on followed by 1700ms off). If the calling tone
    is detected, the modem will negotiate a data call.

 8. If neither a CNG nor call tone is detected, the modem will do nothing and
    treat the call as a voice call.


DETERMINING IF SILENT ANSWER IS SUPPORTED

As mentioned earlier, Silent Answer is currently used in only
SupraFAXmodemsTM. The command to determine if Silent Answer is supported in a
Supra modem is ATI10. The results from the AT10 might look like the following.

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104,115,120,121,123,140,141,142,143,144,146,147,149,150,151,153,154,157,190

SupraFAXModem 288


101=Class 1 FAX           104=Class 2 FAX           115=V.17 14.4Kbps FAX
120=World Wide support    121=V.23                  123=Blacklisting
140=V.32bis 14.4Kbps data 141=SilentAnswer          142=CallerID
143=MNP10                 144=MNP10/Cellular        146=AT\S config display
147=V.FC 28.8Kbps data    149=V.FC 24.0Kbps data    150=Enhanced &F options
151=Enhanced rate control 153=V.34 28.8Kbps data    154=SilentAnswer Plus
157=RINGING response code 190=FLASH memory
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Some older Supra modems will only report the feature number, so notice that
Silent Answer is feature 141 and Silent Answer Plus is feature 154.

SETTING UP SILENT ANSWER

Silent Answer needs to be set up differently depending on whether you are
using Silent Answer or Silent Answer Plus. The following examples will assume
the use of fax Class 1.

There are two possible modes in which Silent Answer can operate. The first
mode enables both Silent Answer and Adaptive Answer. This mode is activated by
sending AT+FAE=2 to the modem. The Supra manual states that Silent Answer
takes precedence over Adaptive Answer. In light of that, there seems to be no
benefit to enabling both Silent Answer and Adaptive Answer at the same time.

The second mode enables Silent Answer only. This mode is activated by sending
AT+FAE=3 to the modem. A slight variation of this mode is called Silent
Answer Plus. This mode is activated by the command AT+FAE=4.

In terms of setting up PROCOMM PLUS for Windows 2.11 to use Silent Answer, 
there are two options. The first is to use "normal" Silent Answer (+FAE=2 or
+FAE=3). This set up requires you to add a +FAE=2 or +FAE=3 to your data
initialization string. 

SETUP FOR FAX CLASS 1 SILENT ANSWER

After making the change to the data string, you then need to set your Auto-
Answer Options to Fax. Set the Rings to Answer field to 3 to 5 rings more
than what you or your answering machine will answer on.

The second option is to use Silent Answer Plus (+FAE=4). Using this mode
requires you to change your Adaptive Answer Command in Fax Connection. Simply
change AT+FAE=1^M to AT+FAE=4^M.

SETUP FOR FAX CLASS 1 SILENT ANSWER PLUS

After making the change to the adaptive answer command, you need to set your
Auto-Answer Options to Data and Fax. Set the Rings to Answer field to 3 or 5
rings more than what you or your answering machine will answer on.

Now you need to set up the answering machine. This setup is the same whether 
you are using Silent Answer or Silent Answer Plus. The set up simply requires
you to record an Out Going Message (OGM) with at least three seconds of
silence before the actual message. Three seconds is simply a good starting
point. If you have trouble, you may need to increase the amount of silence on
the OGM.

In order to use Silent Answer, your answering machine must be the type that 
automatically stops when an extension is picked up. If your answering machine
keeps playing when you pick up the phone, you will need to purchase a device
that stops it. Radio Shack sells a device called a Teleprotector (P/N 43-107)
that will do this.

PROBLEMS WITH SILENT ANSWER

Use the list under About Silent Answer to try to determine where the problem 
occurs. You may need to extend the length of silence on the OGM if the tones
are never being detected. If you have trouble with sporadic performance, try
switching the fax class to Class 2 in Fax Connection. You need to be sure to 
change the Silent Answer Commands in Fax Connection or in the data
initialization strings when you do this. If you are using Silent Answer,
change the +FAE= in the data initialization string to +FAA=.  If you are using
Silent Answer Plus, Change the Class 2 Adaptive Answer command to AT+FAA=4^M
in Fax Connection.  

To quote the Supra manual: "Silent Answer is relatively new, state-of-the-art 
technology; some people find that they need to experiment before Silent Answer 
works well for them."

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         Copyright (c) 1996 Quarterdeck  All rights reserved.
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