CES SUPPORT 407-679-9440
Page 10
MAN71© CES 2010
Important Note
The 4700VP requires a signal from the radio receiver to determine the presents or absence of a mobile carrier, i.e. when the
channel is busy or not. This is accomplished in one of two ways.
1.
The 4700 has an internal squelch circuit to determine channel activity. This circuitry only functions if the receive audio
connection (pin 2) is connected to the
discriminator
of the radio. The discriminator provides
un-squelched
and unfiltered
audio for the 4700’s squelch circuitry and audio that is fed to the phone line. This setting is factory default and is referred
to as internal COR operation. See page 11 for COR adjustment.
2.
If a squelched audio source (speaker audio) is used for pin 2, then an additional wire called External COR (pin 8)
MUST
BE CONNECTED
. This signal is a DC signal that changes in level when the squelch control of the radio is opened or
CTCSS is decoded. This signal can usually be obtained from the radios squelch circuitry or busy channel indicator. This
signal can also be obtained from the CTCSS decoder if so equipped. When this connection is used, the 4700VP must be
programmed for External COR (program code 40) and the correct active state set (code 41). See page 18 for External COR
polarity.
Both of the connections talked about above are very often not available from a radios accessory jack and usually requires an
internal connection to the radio.
Correct operation of DS5 (4700VP COR /channel activity LED) is essential for proper
operation.
In Short, the COR LED must be normally OFF, and only come on when the radios receiver is actively receiving a
signal / carrier.
