The pitch signal derived from a good pitch extractor is a time function that sometimes varies very rapidly, but usually varies very slowly. Using a pitch extractor that produces an 8-bit linear code proportional to pitch period at a rate of 150 times/sec, it is possible to transmit the entire message (ostensibly 1200 bit/sec) with approximately half the total number of bits by making use of the slowly changing parts of the function. The basic principle is to transmit a short code when a probable pitch period occurs and a long message when an improbable period occurs. The probable messages are those representing little or no change from the last period. The rate reduction achieveable this way is better than two to one with exact preservation of the message, but this requires a considerable delay and buffer storage. Instead of this approach, we tried to optimize our code for a given bit rate, keeping the required delay as small as possible. We found that, at a rate of five-eighths or 750 bit/sec, we could choose code words so that a buffer length of 144 bit was sufficient, corresponding to a delay of 60 msec in a 2400-bit/sec vocoder. We use seven codes to indicate small changes, i.e., 0, ±1, ±2, ±3, and an eighth code to indicate that a large change has occurred, followed by the new pitch value. If the buffer is near overflow (an event that occurs on the average of only once in 10 min of an active monolog), the 0 change code is sent, and this represents the only possible deviation from a perfect reproduction of the pitch message.