Model 251A Deluxe Signal Tracer Reference Data, Power requirements. 105-125v AC cps, Power consumption 55 watts. Isolation 1. Specially designed electrostatically shielded power transformer isolates unit from AC line for safe use on AC-DC equipment, C. Input impedance, 1. Probe is 4. megohms shunted by 2mmf. at low frequenoie The input resistance decreases with increasing frequen cy caused by dielectric losses. 2, Audio input impedance is £ meg. on xlOO position, and .25 meg, on xl, D, Frequency response, 1. Probe from 20 cps, to over JOOmc, Note: When probe is used on audio frequencies a slight signal distortion in speaker is normal. 2. Audio inputs from 20 cps. to over 20,000 cps. E* Rosponse characteristics. 1. Audio input to meter xl position flat within ,1 of on* db. from $0 cps. to 20,000 cps, 2. In xlOO position plus or minus db. from 50 ops • to 10,000 cps, 5. Probe flat within 1 db. from 20,000 cps. to 100 me. approx. Above 100 me. the curve depends on the resonance of the ground lead circuit tuned by its length, F. Sensitivity, 1. Probe is li microvolts for full scale deflection, G. Tvtbe complement. 1. 6AQ6/6AT6 high gain triode in probe, 6SJ7 pentode amplifier, 6k6gT power output, 0SN7OT VTVM, 0X5GT reotifier, 2. Standard tubes may be used for replacement.