Determines whether the carrier is present by querying the state of the Carrier Detect (CD) line. Carrier Detect is a signal sent from a modem to the attached computer to indicate that 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 is also known as the Receive Line Signal Detect (RLSD). This property is not available at design time and is read-only at run time.
object.CDHolding
The parts of the CDHolding property syntax are described in the following table.
| Part | Description |
|---|---|
| object | An object expression that evaluates to an object. |
The settings for the CDHolding property are described in the following table.
| Setting | Description |
|---|---|
| True | Carrier Detect line is high. |
| False | Carrier Detect line is low. |
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.
Note 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 (drop the carrier) at any time.
The Carrier Detect is also known as the Receive Line Signal Detect (RLSD).
Boolean