Installation Manual

7
Operation
There are three important functions that the Digital Feedback Terminator performs:
1. It eliminates feedback by recording the incoming page, then playing it back.
2. It is able to repeat a page once, allowing for a better response in noisy environments.
3. It is capable of stacking up to 16 incoming pages by recording incoming pages while playing back
previously recorded pages, on a first-in, first-out basis.
Other important features include the ability to record or block DTMF tones used for zone selections and
external control of system playback.
The DFT120 is designed to run either automatically or through external controls. For most paging applica-
tions, the DFT120 will run automatically. This configuration requires minimum installation time since it is the
factory's default setup. RJ11 connectors are used for Audio/Control inputs and outputs. Where logical,
certain control signals will be provided on the individual RJ11 connectors associated with each.
Page Operation
Recording a Page
A combination of the Page In interface switch and setup switches 1 & 2 determine how the DFT120 records
a page. The DFT120 is always monitoring for loop current or contact closure, depending on the Page In
switch setting. By configuring setup switches 1 & 2, the DFT120 can be configured to start recording a page
into memory only on loop current detection or only on contact closure detection. It can also be configured to
detect either of the above and then wait before recording a page into memory until a DTMF digit is detected.
This configuration provides for excellent DTMF signaling into a zone paging device.
For telephone systems that cannot provide a loop start or a contact closure, the DFT120 can be triggered
solely by audio detection. In this configuration when audio is detected the unit begins recording the page into
memory. After a 3-second interval of silence, the DFT120 stores the page and begins playback of the page
as soon as it is possible.
Loop Start Interface (Page In switch set to LS)
• Loop Start Activation (Setup switch settings UP, UP) - Begins recording page into memory as
soon as loop current is detected.
• DTMF Activation (Setup switch settings DN, UP) - Begins recording page into memory
when loop current is detected and then a DTMF tone is detected. This
provides for better DTMF signaling to zone paging devices.
Dry Audio with
Contact Closure Interface (Page In switch set to DL)
• Contact Closure Activation (Setup switch settings DN, DN) - Begins recording page into memory as
soon as a contact closure is detected.
• DTMF Activation (Setup switch settings DN, UP) - Begins recording page into memory
when a contact closure is detected and then a DTMF tone is detected.
This provides for better DTMF signaling to zone paging devices
Dry Audio without
Contact Closure Interface (Page In switch set to DL)
• Voice Activation (Setup switch settings UP, DN) - The page is recorded into memory as
soon as audio is detected. After a 3-second interval of silence, the page
is completed and stored for playback.
If either the memory capacity (240 seconds) or the maximum number of paging messages stored (16) is
exceeded, no further page recording can occur. A busy back tone will be heard by the caller when the unit is
accessed under either of these conditions. The recorded message must be a minimum of one second in
length. Any message shorter than one second will be deleted.