These TTL encoders feature priority decoding of the inputs to ensure that only the highest-order data line is encoded. The ’148 and ’LS148 devices encode eight data lines to three-line (4-2-1) binary (octal). Cascading circuitry (enable input EI and enable output EO) has been provided to allow octal expansion without the need for external circuitry. For all types, data inputs and outputs are active at the low logic level.