Abstract: A selection of signals, each to one of a limted number of contacts, achieves both parallel and serial interfaces using a single connector. The connector has individual contacts for the following signals for parallel communications: strobe, data signals, acknowledge, busy, printer out of paper, printer selected, paper feed one line after printing, logic ground, chassis ground, initialize the printer controller, and printer error; and has individual contacts for the following signals for serial communications: transmit data, request to send, logic ground, receive data, data terminal ready, data set ready, and clear to send.

Abstract: A read only memory system with replaceable units is provided in which the replacement units have a variable capacity. In addition, the system is sufficiently flexible so that a replacement unit substituted for an original unit may subsequently be removed from the system once and the original unit restored. The read only memory system has a fixed main read only memory with a plurality of addressable units of uniform capacity in combination with a substitute memory of a greater capacity than the addressable units. A control is provided with the capability of selectively disabling units of a fixed memory. It also can selectively enable a portion of the substitute memory and substitute the enabled portion for a disabled fixed memory unit. The control is also capable of selectively varying the capacity of the substituted enabled unit.