Abstract: A modem to modem communication system supports call waiting services by exchanging hold request and acknowledge signals before relinquishing the line servicing incoming calls. Thereafter, the modem to modem session is reestablished without having to redial. The hold request may be denied or accepted, and may define the duration a modem will hold before hanging up. The holding modem maintains the session by fooling the higher protocol layers, making them believe that the modem is not on hold. Three-way calling services are also used to free up the shared line for outgoing calls while maintaining the session with holding modems. A table may be employed to screen incoming calls through a comparison of the caller ID information with that in the table. The table may be within the modem or the host computer.

Abstract: Nitrilase enzymes are provided which have Km at pH 7.0 for acrylonitrile of 500 .mu.M or below. The enzymes also have Ki at pH 7.0 for ammonium acrylate of at least 100 mM. In particular, the nitrilases have a value of the ratio of the said Ki to the said Km of at least 200. Particularly preferred nitrilases are obtainable from the microorganisms Rhodococcus rhodochrous NCIMB 40757 or NCIMB 40833. These nitrilases can be used in processes of converting acrylonitrile to ammonium acrylate in aqueous or vapor form and for detecting low levels of nitrile in aqueous or vapor form.