Subject: From: Date:

Local Phone Sessions LEC1964.aol.com Fri, 28 Jan 2000 18:48:38 EST

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Joe,
     This might be of some help after upgrading to Windows and the inherent 
loss of the Bigmouth phone interface. The Bigmouth card along with a number 
of other devices that use in-house phones all have one thing in common. They 
replace the phone companys "talk power" with one that they provide. Talk 
power is the DC component of the phone companys service. Without going into 
more detail, phones actually only have 7.5-8.5 volts DC when they are "off 
hook". This voltage creates about 30 to 40 milliamps of current. By replacing 
the phone companys pair with a pair from an equivalent local voltage/current 
source a phone will become fully functional for both voice and DTMF tone 
(Touchtone) transmission/reception.
     This is can be done with a relay. Using a DPDT relay the center or 
movable contacts should be wired to the phones to be used for the local 
sessions which also includes the modem. The normally closed when 
de-energized, non-movable, contacts  should be wired to the phone company. 
The non-movable contacts that "make" on energization of the relay coil should 
be wired to a local power source. This local power source could be as simple 
as a plug-in 12 volt DC  transformer using appropriate current limiting 
resistors. Polarity must be observed. Normally the color code used for the 
phone wiring for line 1 is red and green. Red is negative. Green is positive.
     When a local power source, at least one phone, and a modem are all 
connected a local/remote phone session is possible. If Phone-Interface-C is 
set to "answer" ECS thinks it's answering a remote phone call but of course 
it's not. In fact, you will first have the opportunity to even leave a 
message. Some ECS users have indicated that they leave phone messages for 
other household members and this is an extra benefit that is available with a 
remote phone session. A touchtone entry # will start the interactive session.
     There are several methods that can used to energize the phone transfer 
relay and to notify ECS that a phone session should commence. A PLC (X-10) 
pushbutton command could be used to notify ECS. A touchtone decoder could 
also be used.
     I have to admit that I don't use local phone sessions but I was curious 
to see if it was possible and how efficient this method of interactive 
control really is. Since there is a "home run" of my phone service to my 
security panel and also 12 volts DC available at that location (security 
backup battery) I placed the transfer relay there. It took less than an hour 
to do the wiring and since I had a relay there was no cost. Two 68 ohm 
resistors (one in each conductor) limit the current to about 35 milliamps. I 
use a programmable four output touchtone decoder to notify ECS. The decoder 
uses a standard modular telephone connector and has screw connectors for its 
four relay outputs.
      Picking up any phone in the house will initially provide standard phone 
service and access to the phone companys "switched network". However, if any 
one of the four unique two button touchtone codes are entered, a relay 
contact on the decoder will close and ECS is notified via a Micro Redac 
digital input. ECS will then respond by using a Micro Redac relay output to 
control and energize the phone transfer relay. A programmed delay is used to 
provide adequate time for "line settling" prior to Phone-Interface-C going to 
"answer".
     In summary I would have to say that this does work reasonably well. 
However  these would be my recommendations. (1) Use a single cordless phone 
and one or two standard phones to minimize the wiring. (2) Wall transformers 
tend to be poorly filtered with no regulation and will produce audible 
background hum. Use a better quality DC power supply. I purchased a quality 
supply for about $25 for use with local SR phone sessions which by the way 
requires the same transfer scheme. (3) I would use phone session macros. 
Since I use abbreviations in Group, Event, and Item descriptions it was hard 
to understand the TTS audio.
     I hope this will help and I apologize for my rambling text.

Larry C.

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