NNTDSP.001 DSP Noise Cancellation Board DSP Noise Cancellation for Icom series of professional two way radios. The NNTDSP.001 DSP board operates on most Icom commercial radios that have an accessory socket (except IC-F12/22 Series, IC-F51/61series and IC-F22SR). The module is installed in the "Option" socket and a small modification is required in the radio to enable the module to work. This modification cuts the audio path of the loudspeaker and allows the insertion of the DSP board. The programming software is set up to "enable OPT 1" on one of the assignable buttons such as P0 to P3 on the mobiles or if used with a handportable there are also the buttons above and below the PTT. Noise level is set at 6; this is adjustable by links on the module. www.bhinstrumentation.co.uk.