# Frequency shift key data functions

NMS boards are capable of sending and receiving frequency shift key (FSK) data. The transmit function is an implementation of the modem portion of Bellcore advisory TA-NWT-000030. The basic modulation is continuous-phase binary FSK at 1200 baud between 1200 Hz (mark) and 2200 Hz (space). The only supported baud rate is 1200. Alternatively, the implementation is based on ITU V.23 FSK at 1200 baud between 1300 Hz (mark) and 2100 Hz (space).

The following functions are used to send or receive frequency shift key data:

Function | Synchronous/ Asynchronous | Description
--- | --- | ---
adiStartSendingFSK | Asynchronous | Initiates sending frequency shift key data.
adiStopSendingFSK | Asynchronous | Stops the sending function.
adiStartReceivingFSK | Asynchronous | Receives frequency shift key data.
adiStopReceivingFSK | Asynchronous | Stops the receive function.

FSK modems are the low-level building blocks for analog display services interface (ADSI). The ADI service does not provide an ADSI programming interface, but you can use the FSK functions to implement ADSI applications.