Abstract: According to the present invention, a hand-held portable transmitter is provided which is capable of communicating with a variety of different message receiving hosts. The transmitter is provided with a technique for generating waveforms to communicate with foreign message receivers over a communication channel by using a lookup table and software implementation in combination with a telephone interface circuit. Also provided is a versatile encoding protocol in which a message is optionally converted to a four-bit, five-bit, or six-bit sequence, or to a sequence of variable-length bit-strings, the converted message is queued and regrouped as four-bit nibbles, and the nibbles are communicated by DTMF tones.