Abstract: This invention relates to a coupler which allows a host processor such as, for example, a personal computer or point of sale device or the like to communicate with and control a portable data carrier. A portable data carrier is a portable device which contains integrated circuit(s). Examples of portable data carriers are Integrated Circuit Cards, data keys, super smart cards, and smart coins. The coupler is adapted to receive the card in a standard card receptacle or card reader to establish connection between the card and a connector in the coupler to which the necessary control signals are applied. The presence of an integrated circuit card is detected in the coupler's card connector terminal which provides a card present signal to the host processor. The host, in turn, provides Clear-To-Send (CTS), Request-To-Send (RTS), Data-Set-Ready (DSR) and Data-Terminal-Ready (DTR) signals.