Installation manual
Duet2 D2600 / Duet3 D2650 Installation Manual – EU-D2600-D2650-INST/A10/v1 - 9
Call Interception (cont’d)
7.1.1.2 Forward before Acknowledge
In this case, the Duet will attempt to forward the call before sending an “acknowledge” to the alarm
control panel. This will cause the alarm control panel to make several attempts to call the Duet.
If the alarm control panel has many Contact ID messages to send, they will be forwarded very slowly,
one call forwarded at a time, rather than using the “follow-on” call technique.
This operation may be improved by using a third technique. This will only forward the first call without
acknowledging the alarm control panel. Further calls within a short period of time will use the “store
and forward” technique. This is accomplished by programming the “Acknowledge Timer” in the
programmer to 5 minutes for example. If this timer is set to 0, then forward before acknowledge will
always operate.
7.1.2 PSTN Priority
The PSTN relay is not energised, so that the alarm control panel is connected directly to the PSTN.
This is the default state when the Duet is not powered.
The Duet monitors the PSTN line and if it fails, switches the alarm control panel to the Duet.
The Duet also monitors outgoing calls of the alarm control panel over PSTN, and if a programmable
number of call attempts fails, will switch the alarm control panel over to the Duet, for a programmable
period of time.
For example, if two call attempts fail and the third is successful, subsequent calls will be attempted
over the PSTN. However, if three call attempts in a row are unsuccessful, the Duet will switch the
alarm control panel to the Duet and intercept the fourth call, and re-transmit it over radio or LAN. In
this event, the Duet will keep hold of the alarm control panel for 10 minutes (or whatever time period is
programmed) before reverting the control panel back to the PSTN.
If the radio path fails, the alarm control panel will remain connected to the PSTN even if a PSTN fault
is detected.
Note: In this mode, if the call is made via PSTN, the SMS text function for alarm control panel calls will
not work.
7.2 Duet Line Simulator
When the Duet is connected to the alarm control panel, the operation is as follows:
1. The Duet provides 42-45VDC to the alarm control panel simulating a telephone line
2. When the alarm control panel goes off hook to make a call, the Duet detects the increased
current and provides dial tone to the alarm control panel (350Hz for maximum of 9 seconds)
3. The alarm control panel dials its programmed telephone number using DTMF (if DTMF is
detected during the 9 seconds of dial tone, the dial tone is switched off). The telephone
number dialled is ignored by the Duet. The Duet will wait 3 seconds for dialling to complete,
then it will give handshake tones to the alarm control panel (the frequencies of these tones are
programmable in the NVM).
Note: if the alarm control panel dials in Loop Disconnect, as long as it takes less than 9 + 3 seconds to
complete, it will be ready to accept the HS tones from the Duet, after the 12 seconds have elapsed.
The alarm control panel will send Fast Format or Contact ID data.
4. If the Duet receives no DTMF in response to the Fast Format handshake, it will repeat it. If it
still gets no response, it will send out a SIA handshake tone, and wait for SIA FSK data.
5. The Duet will store the received data in its NVM and signal an “Acknowledge” tone (which is
programmable) to the alarm control panel (if the “forward immediately” option is selected, the
ACK is not sent at this time).
6. Once a data message has been transferred to the event log NVM, the Duet will commence its
signalling function via GPRS, GSM, LAN and/or SMS, depending on programming. Once the
signalling is complete, the Duet will mark that data message as being sent.
7. A preferred path may be selected, either wired or radio. If three calls to the preferred path fail,
the Duet may call via other paths, and rotate between them until a successful call has been
made. In the unlikely event of all calls being unsuccessful, the Duet will operate a “Fault” relay
output. This output may be connected back to the HCP or to any other equipment. This
output will remain active until a successful communication has occurred, or the Duet is reset.