have transmission rates from 50 bps to 56 kbps. The service can be either dial accessed, or con- nected via dedicated line. Use charge is based on the number of kilo packets. Each kilo packet contains 128 characters. The data communications planner should make a realistic estimate of actual data rate required, usage expected in connect time, the amount of data to be transferred, and the distance involved. These factors, properly evaluated, will allow selection of the most cost ef- fective service for transmission. 7.3 FACSIMILE SERVICES Facsimile services are generally available from one of the established common carrier companies and permit user access to their net- work for the purpose of transmitting fax copies. This can be a cost- effective alternative to designing one's own facsimile network in that the carrier company provides all that is needed in the way of switch- ing and control hardware; the user needs only to have a facsimile terminal. Other advantages of the facsimile service come in the way of reduced line rates, or even distance-insensitive flat-rates covering the entire country. Some of the currently available facsimile services are included in the following paragraphs. 116 TELECOMMUNICATIONS FAXPAK is operated by ITT domestic transmission systems. This service provides store-and-forward communications between com- patible as well as many incompatible facsimile terminals. Available in the continental United States, the service is priced per minute on a "delivery priority" basis (15 minutes or 2 hours). This convenient structure offers lower sending costs for lower priority demands, and allows the user to make overnight transmissions at lower rates. Sub- scribers can access FAXPAK switching centers via analog or digital private lines or public dial-up lines. Graphnet, a subsidiary of Graphic Scanning Corporation, is an authorized special common carrier that began its Fax-Gram facsimile service in January 1975. Available on a national basis now, the tar- iffed service is based on a value-added netwo