Keycode Receiver

Keycode Receiver (KR) provide in-band DTMF and MFC (R1 and R2) detection on TDM timeslots from the TDM switch. MGU2 supports connecting KR in serial or parallel to the PCM stream. Serial connection is usually only applicable to DTMF tones, when in-band detection is used, e.g. for mobile extension calls.

Connecting KR in serial makes it possible to remove (see note below) the DTMF tones from PCM stream, but adds an extra latency of about 65 ms per default, which can cause echo problems in certain conditions. It is possible to have alternative settings to lower latency to as low as 16 ms at the cost of DSP channel density. See section Keycode Receivers & Senders.

Note: When KR removes a DTMF tone there might be a leakage of less than 20 ms, thus may be audible but not detectable by any standard compliant DTMF receiver. Currently, there is no way to enable "complete removal" for KR as it is for DTMF receiver in VoIP channels.

In parallel KR connection, virtually no additional latency is imposed by KR, but DTMF tones are passed through the PCM stream.

Selection of serial/parallel connection is controlled by MX-ONE Service Node when KR connection is ordered.

KR is a dynamic resource in the MSP and number of available resources depends on actual usage and load of the MSP.

The KR in MGU2 is normally used in Mobile Extension (ME) calls. Currently, serial connection is used to by default setup KR for ME calls, thus each ME user will have an extra delay of about 65 ms in their speaking path.