To assist in users in programming their radio, the D-STAR calculator lists all of the repeaters and modules available and allows you to specify the source and destination that you want to talk to. This button allows the calling user's information to be inserted into call sign memory and therefore program the radio to respond to the caller. Many Icom radios implement what has been called the "One touch" or RX-CS button. If the station that you want to contact switch between bands or switches between repeaters, it might take time for the system to find the user’s location.
One issue with this is that the updating process is not fast, sometime taking an hour to update a position. If I specify that I want to talk to an individual call sign, the Gateway Servers will determine the last repeater and module on which that user was heard and route the signal to that location.
To allow for an easier means to reply, the D-STAR gateway implements a “Where is he” function. Unless the source radio operator tells the destination radio operator where they are at, the destination radio operator cannot determine the location to respond to. When someone tries to talk back, they must configure their radio to route their signal to the same repeater and port as the source radio. When using this method, only the source radio’s signal path is specified. When a gateway computer and an Internet connection is added, a user can send their signal to another port on any other gateway connected repeater. A user on VHF could send their signal to another port on the same repeater when using only the local controller. The original implementation of the controller and gateway allowed for the source radio to specify where its signal should be sent. Linking is accomplished by the repeater controller, the gateway server and just recently the reflector.