Abstract: A modem for interfacing digital data communications between a data processing terminal and a telephone link contains, in the modem front panel, a control switch configuration for effecting automatic dialling of a previously stored telephone number, thereby enabling the automatic placement of a call for either an asynchronous or synchronous terminal which cannot perform modem command language. As an additional feature the modem of the present invention provides the capability of allowing an asynchronous terminal, using the command language of the modem via a first asynchronous interface, to place a call for either a synchronous terminal or an asynchronous terminal which cannot support the modem command language and, as a result, is connected to a second interface. The first interface is coupled to a modem control processor through which communication commands for the operation of the modem are effected.