19.6. Example 5: Contact to Contact relay
In a few instances it may be necessary to transmit the status of a contact to a remote point. Let us
use an alarm as example. If the alarm at your home sounds, you may want a warning light to switch
on in a remote location and a voice call to be placed to a specified number.
For this example, we will use two GSM commander units, one at the local alarm system, and another
at the remote location.
Local GSM Commander Hardware:
We connect the alarm output (12V signal that drives the siren) to one of our inputs as described in
section 6.8. The positive wire from the alarm panel is connected to the +IN terminal, and the
negative wire is connected to -IN.
Local GSM Commander Configuration:
Using the setup software, we create the following behaviour statements:
St1 : IF
Input Goes Active
THEN
send “alarm on” via SMS to +27833341234
St2 : IF
Input 1 Goes Active
THEN
Place Voice Call to +27821121323
St3 : IF
Input 1 Goes inactive
THEN
send “alarm off” via SMS to +27833341234
The above 3 statements detail two actions to trigger in the event that the input goes active. One is
an SMS message to the remote unit, and another is a voice call to a cellphone. In the above
statements, +27833341234 is the number of the GSM commander at the remote location.
Remote GSM Commander hardware:
We use a second GSM commander unit at the remote location. Here we connect the warning light to
output 1 of the GSM Commander so that if the relay is activated, the warning light will turn on.
(exactly as described in section 6.9)
Remote GSM Commander configuration:
The configuration of the remote unit will be similar to example 2 (control an appliance). Using the
setup software, we create the following behaviour statements:
IF
Message is received containing “alarm on” from any listed number
THEN
Activate Output 1.
IF
Message is received containing “alarm off” from any listed number
THEN
Deactivate Output 1.
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