Call parking is a feature that allows a person to put a call on hold at one telephone set and continue the conversation from other telephone set.
The “call park” feature is activated by pressing a preprogrammed button (usually labelled “Call Park”) or a special sequence of buttons. This transfers the current telephone conversation to an unused number and immediately puts the conversation on hold. (This is called parking the call; and the call is said to have parked onto a certain number or channel. Essentially, call parking temporarily assigns an number or channel to an incoming call.) The call can later be retrieved.
Following scenario is an example of call parking.
If the desired called party is not the person who picked up the call, and the desired called party is at another location, the person who picked up the call may park the call and then asked the desired called party to retrieve the call.
For example, Karen is an assistant and Holly is her leader/boss. If Karen picks up a call whose desired called party is Holly, Karen can park the call and say "Holly, you have a call parked on channel 1" and Holly would dial special number to access the call on hold.
Some of above descriptions are from WikiPedia website.
In MSS, this service is supported from version 2.10 and it is seperated to two services:
"call park" service is used by local users to park the incoming call. When one person wants to park the incoming call, he/she can transfer the call to "*70*n". "*70*" is the special number prefix for parking call. "n" is the channel number, it is between 1 and 99. That means the MSS can permit at most 99 parking call at the same time. In above scenario, Karen can dial "*70*01" to park the call on channel 1.
Once the call is parked, the caller party will hear music. A set time is then provided for any person to retrieve the call on other telephone set. By default, the time value is 60 seconds.
If no one retrieves the parked call within the set time, MSS will release the parked call.
"call retrieve" service is used by local users to retrieve the parked call. When one person wants to retrieve the parked call, he/she can dial "*71*n". "*71*" is the special number prefix for retrieving call. "n" is the channel number where the call is parked on. In above scenario, Holly can dial "*71*01" to retrieve the call which has been parked by Karen.
In MSS, only the person who has "call park" service right can park the call, and only the person who has "call retrieve" service right can retrieve the call.
So what we should need configure is the services right in local user configuraiton. Following figure describes the configuration.