Those dots would be the right places for copying high tone RTTY using 2125 and 2295 (170 Hz shift) or 2125 and 2975 (850 Hz shift) tones. Just about 1 KHz further outside the pass band than the standard crystals. 73, K0CQ, Technical Advisor to the CRA -- Entire content copyright Dr. Gerald N. Johnson, electrical engineer. Reproduction by permission only.