CDHolding

This property queries the state of the carrier detect (CD) line to determine if the carrier is present.

Syntax

object.CDHolding

Parameters

object

Object expression that evaluates to a Comm control. Following are the settings for the CDHolding property:

True

Carrier detect line is high

False

Carrier detect line is low

Remarks

The CDHolding property is read-only at run time. It is unavailable at design time.

Carrier detect is a signal sent from a modem to the attached computer that indicates the modem is online. When the carrier detect line is high (CDHolding = True) and times out, the Comm control sets the CommEvent property to comEventCDTO (carrier detect timeout error), and generates the OnComm event. The carrier detect also is known as the Receive Line Signal Detect (RLSD).

It is especially important to trap a loss of the carrier in a host application, such as a bulletin board, because the caller can hang up—that is, drop the carrier—at any time.