HP TM 11-6625-2779-14&P manual 0dBm, Input jacks are connected in parallel. If a 600 ohm, 135 BAL

Section III Model 3555B

	Figure 3-8. Simple Test for Inductive and Capacitive Coupling
0dBC = 0.775V across any impedance as read on an			3-70.	The		3555B	comes	equipped		with	all the
-hp- Model 400D AC Vacuum Tube Voltmeter. Thus,			necessary parts for converting the 135 BAL function to a
the dBC is strictly a relative term.			150	BAL	function.		The	following	is	a	simplified
3-66.	Measurements can easily be made in dBC.	by	procedure for making the modification.
utilizing the Model 3555B Telephone Test Meter.		To		a.		Remove the set from the case and remove
make these measurements, set FUNCTION to 600 and						the FUNCTION board.			Clip the shorting
the INPUT switch to TMS BRDG. Any termination						wire from across A1R17 (see Figure 7-2)
required other than 600 ohms must be provided						and reinstall the FUNCTION board. Leave
externally and connected across the two binding posts T						the set out of the case.
and R.	Termination can also be made using a patch			b.		Set the 3555B controls as follows:
cord and any one of the other INPUT jacks since all						RANGE	..........................................				0dBm
INPUT jacks are connected in parallel. If a 600 ohm						FUNCTION				135 BAL
termination is to be used, the internal termination can be						INPUT				TMS TERM
utilized by placing the INPUT switch to the TMS TERM				c.		Remove the 150 BAL decal from the
position.						envelope supplied with the set.					Remove
3-67.	MEASUREMENT PROCEDURES.					the backing from the decal and place it
3-68. Tables 3-3through 3-8list the step by step						over the 135 BAL function pushbutton.
procedures for measuring levels and noise balance,				d.		Connect a 150 ohm balanced source to the
recorder calibration and transmission loss using the						input of the 3555B at a level of 0dBm
3555B. For a more detailed discussion on level and						(387mV rms) at a frequency of 1kHz. Turn
noise measurements refer to paragraphs 3-12through						the 3555B ON and adjust A3R24 (Figure 7-
3-47.						3) for 0dBm indication on the 3555B meter.
3-69.	150 BAL CONVERSION.			e. Reinstall the set in its case.
			3-12