We consider the discrete-time channel with intersymbol-interference and additive noise under output analog-to-digital conversion (quantization) at the receiver. The analog-to-digital converter is optimized so as to maximize the information rate between the quantized channel output sequence and the channel input sequence, where the input sequence has independent and identically distributed symbols. An upper bound on the information rate is derived. Simulation results demonstrate the effectiveness of the designed quantizers over conventional quantizers at 1-bit/sample precision. The advantage of those quantizers is further emphasized by an example of a channel for which a simple slicer and a carefully optimized channel input with memory fail to achieve a rate of one bit per channel use at high signal-to-noise ratio, in contrast to memoryless binary signaling and an optimized quantizer.