Multi-Tech Systems MMCModem GPRS (MTMMC-G) - Manual (Page 87)

Chapter 10 – Supplementary Services Commands
Multi-Tech Systems, Inc. Wireless GSM/GPRS AT Commands (Document Number S000293I) 87
Call Related Supplementary Services +CHLD
Description: This command manages call hold and multiparty conversation (conference call). Calls can be put on
hold, recovered, released or added to a conversation.
Values:
0
Release all held calls or set User Determined User Busy (UDUB) for a waiting call.
1 Release all active calls (if any exist) and accepts the other (held or waiting) call.
1x Release a specific call X (active, held or waiting)
2
Place all active calls (if any exist) on hold and accepts the other (held or waiting) call.
2x Place all active calls on hold except call X with which communication is supported.
3
Adds a held call to the conversation.
4 Connects the two calls and disconnects the subscriber from both calls (Explicit Call Transfer).
Syntax: Command syntax: AT+CHLD=< n >
Command Possible responses
AT+CHLD= OK
Note: If n is within the defined values
AT+CHLD=? +CHLD: (0-4, 11-17, 21-27)
OK