HT dd is a provider of products and services such as trunked radio service providers,software, website load distribution,telephone accounting and billing systems,broadband wireless access systems (bwa),telephone ringing machines,call announcers for telephones,telephone announcement systems, recorded,information systems, telephone, voice activated,telephone impulse transmitters, automatic,telephone intercommunication systems, railway,telephone intercommunication equipment, aircrew,telephone intercommunication equipment, sub-sea,telephone intercommunication equipment, flameproof.