HP TM 11-6625-2779-14&P manual Level and Noise Measurements, Level Measurements

Model 3555B Section III

Table 3-1. Front, Side and Rear Panel Controls, Indicators and Connectors (Cont’d)

2.135: Selects the input circuitry for 135

ohm balanced circuits. A high frequency transformer is selected for this function.

3.75: Selects the input circuitry for 75 ohm unbalanced operation. Only the 75 ohm jack can be used for this function. This function does not utilize an input transformer, therefore the maximum bandwidth is available on this function. This jack accepts a 358 plug.

(10)DIAL/AC MON: A set of multiple jacks accepting Western Electric type 310 or 347 plugs, 289 dual plugs and a pair of special clip posts marked T and R which accept a Western Electric 1011IB lineman's handset for the dial and talk operation when the FUNCTION pushbutton marked DIAL/BAT is depressed. Loop dialing is used and the circuit must supply talk battery. When any other FUNCTION pushbutton is depressed, the tip and ring of these jacks are connected to the AC MON output of the internal amplifiers for monitoring purposes.

(11)DC MON: Accepts a Western Electric 310 or 347 plug for tip negative and sleeve connections to an

external dc recorder. Output voltage is proportional to the input voltage on any one setting of the RANGE switch.

(12)INPUT: A set of multiple jacks accepting Western Electric 241 (or 289), 309, 310 and 358 plugs and a pair of binding posts marked T and R for banana plugs, spade lugs, phone tips or bare wires

providing connection to the input circuitry of the measuring set. When the DIAL BAT pushbutton is depressed, the INPUT jacks are connected in parallel with the DIAL/AC MON jacks.

(13)Battery Cover: Removeable by four 1/4 turn screw fasteners to expose the internal battery for replacement.

(14)48V 310: A jack accepting a Western Electric 310 plug with tip negative and sleeve ground to supply external office battery power to the set. Insertion of a 310 plug into this jack disconnects the internal battery. The BAT-AC switch (16) must be set to BAT for office battery operation.

CAUTION

WHEN OPERATING FROM AN EXTERNAL BATTERY, CORD SHOULD BE CONNECTED TO MEASURING SET FIRST, THEN PLUG INTO BATTERY SUPPLY TO AVOID SHORTING THE OFFICE BATTERY.

(15)0.15A-SPARE Fuse: A 0.15A slo-blo fuse and a spare for measuring set protection when operating from AC power. Fuses are not used when the set is battery powered.

(16)BAT-AC Switch: A slide switch for selecting the ac power source or the internal battery and office battery jack, (14), power source. The switch may be operated by a small screwdriver or pointed tool inserted into the slot in the switch.

(17)AC Power Receptacle: A 3 prong power receptacle for the special power cord stored inside the front

cover. The BAT-AC switch (16), must be positioned to AC for this power source.

3-11. High storage temperature is damaging to dry cells and tends to reduce shelf life. Low storage temperature is beneficial to battery life although the battery should be warmed to room temperature prior to use. Turning off the set when not in use and consideration of the above factors will maximize battery life. The instant turn characteristics of this set with no warm-up time required allows turning off between measurements.

NOTE

If the battery voltage indication drops below the left end of the arc on the meter face the set will not operate properly. This will be noted by a slow oscillation of the meter. If this symptom is encountered, depress the DIAL/BAT pushbutton and check the battery condition. If the indication is to the left of

the arc on the meter face, replace the battery.

3-12. LEVEL AND NOISE MEASUREMENTS.

3-13. Since the 3555B is both a level measuring set and a noise measuring set, the procedure for making these measurements will be treated separately. Level measurements can be made at voice frequencies and carrier frequencies. Since the procedure for making voice and Carrier level measurements are identical except for the FUNCTION pushbutton utilized, only one procedure will be described in detail.

3-14. LEVEL MEASUREMENTS.

3-15. The 3555B can be used as a wide range and wide

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