The IBM/Rolm (now Siemens/Fujitsu) Rolmphone 120D, showing the RS-232C DB-25 data connector on the back, and to its right the DTR, RxD, TxD, and Power lights. Left of the DB-25 is the socket for the Data Communications Module (DCM) power supply, which had to be plugged into a wall socket. The phone jack is above the DB-25; works only with the Rolm CBX. The phone allows simultaneous voice and data calls. Maximum data communication speed: 19200 bps. Flow control: none. Having the lights in back was not terribly useful; some people put mirrors behind their phones so they could see them without turning the phone around.