Check the listing for details. Integrated Systems Technology Tel-Com 150A Mobile Briefcase Telephone Paperwork. Condition: Used. Listed at 315.99 USD. Integrated Systems Technology TEL-COM 150A Mobile Briefcase Telephone -Paperwork For sale is a Tel-Com 150A briefcase phone. Serial number is 1161, out of total production of just over two thousand. The Tel-Com 150A was the first completely portable battery powered dial telephone. This was a 25 watt IMTS (Improved Mobile Telephone Service) type mobile telephone that had direct dial capability. It was developed in the USA, around the year 1973. Approximately 2,100 were manufactured in Garland, Texas by Integrated Systems Technology and cost $3,500 each. Tel-Com sold a number of these phones to celebrities of the era and executives such as those in the oil business. This phone is an antique and has not been tested for functionality in any way.