Frequency is measured in hertz (Hz). A person who has hearing within the normal range can hear sounds that have frequencies between 20 and 20,000 Hz. The most important sounds we hear every day are in the 250 to 6,000 Hz range.
An issue date was added, and cheques may not be valid a certain amount of time after issue. In the US and Canada a cheque is typically valid for six months after the date of issue, after which it is a stale-dated cheque, but this depends on where the cheque is drawn; in Australia this is typically fifteen months.
Article 4 of the Uniform Commercial Code, or UCC, outlines check processing standards and procedures for U.S. banks. It states that banks don't have to accept a stale check -- one that is more than six months, or 180 days, old. After six months, the odds of being able to collect a stale check drop. However, not every stale check gets rejected; tellers often overlook dates.