Version 6.2 237 February 2011
SIP User's Manual 8. IP Telephony Capabilities
8.2.4.2.1.3 DID Wink
The device's FXO ports support Direct Inward Dialing (DID). DID is a service offered by
telephone companies that enables callers to dial directly to an extension on a PBX without
the assistance of an operator or automated call attendant. This service makes use of DID
trunks, which forward only the last three to five digits of a phone number to the PBX. If, for
example, a company has a PBX with extensions 555-1000 to 555-1999, and a caller dials
555-1234, the local central office (CO) would forward, for example, only 234 to the PBX.
The PBX would then ring extension 234.
DID wink enables the originating end to seize the line by going off-hook. It waits for
acknowledgement from the other end before sending digits. This serves as an integrity
check that identifies a malfunctioning trunk and allows the network to send a re-order tone
to the calling party.
The "start dial" signal is a wink from the PBX to the FXO device. The FXO then sends the
last four to five DTMF digits of the called number. The PBX uses these digits to complete
the routing directly to an internal station (telephone or equivalent)
îš„ DID Wink can be used for connection to EIA/TIA-464B DID Loop Start lines
îš„ Both FXO (detection) and FXS (generation) are supported
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