Lowilqdmceandcanbetlnneduploud | Telex RM300, CM300 specification

23 millipmpms for tbe CM300/RM300, 33 millirmperes for tbe CM300URM300L).

The ability of hadphones to shut out mwmted envi- Euviroampf Table 2-1 shows typical opentino ~talaoigvaiesfromnons(odBisolation)to . bout

=ts	and tbs	o f o	f	mi= p d .	1/8th as ioud (30 dB isolation).		The degree of isolation
					depads both on the design of the bssdset sad the
A very quid openting mvhmnmt,			such as a television		h p a c y colltmt	of the	m h t a l noise.
studio,	may require that Damd does not leak from the				Lightweight, 'opm'	hesdsetg such as the RTS System

headphones, meanbig the badphoaes should have good Lt1267 (single muff) md LEI268 (double muff), have

'acoustic isolation'.	plmwt no (0 dB) isolation. The trade-offis that the
	LH267/LH268 am very comfortable and can be worn for

A very noisy or Loud mvironmat usually requirts long Mods (8 to 12 hours) without physical d i d &

headphones tbat prevent outside muud from ledring in		fromtheeandfsorlwndbd. TheLH267/LH268are
(again,	gwd rcwatic isolation), h e a d p h that can	lowilqdmceandcanbetlnneduploud.
pmQes a loud, dor d,lad noist ancelliag mi-
cmph-,	aswell.
U ~ g ~ i n a n o i s y m v i m a m a n t ~ ~
theaormd!iumtheheadphoapisasloudorlouderthmtbe		The DT108lDT109 headmt6 have m isolation m g b g from
sound	l d i n g into the headphmes from the noisy	The DT108lDT109 headmt6 have m isolation m g b g from
en-		1odEtomdB.

~~ g e a o n l , ~ - ~ f ~ h s ; l d p h o a e d c p c a d s upon its ability to ho& powar at a givm voltage

(impdame) and the efficiency of its design. Practically.

theimpdwxhasalargerefhxtwith~tdaybeulstts.

L a v ~ o e ~ u e l o r d e r , & g

theluorstltiontodnwmncwrrntfromthepower

supply. High hqdmce hadplmss am not as l a d ,

dmuing lcss t- from tbs paves apply. The user

s t a t i o n d s s i g n m g s o f ~ f o r t h e b e r d p h o a s p r t

of the hadsat is 25 ohms to 600 ohms. Head-

~ M X ) t o U X X ) o h r m w i l l o p n t e a t I s d u w d

levels. InadoublemuffhadsetruchastheBcyerDT109

sold by RTS Systems, them u e 50 ohm h a d p h e s eoa-

nected inparallel d t i n g in mimpedaaca of 25 ohms.

Efficiencv The user station pmd- the loud& sound in low impdwx headplmw svch as the DT109. In this

headphone, ons milliwatt of dcchical power produce 94 dB SPL (soundFlwsIUa Level).

At last four companies, Telex, Sstcom, David Clark, and

Cuter Eagbmhg adl kadscts intended for heavy iduskid, .aosl#rc, mdmilitmy mark&.. Thcsc hdsets

ern p V i & d c isohtion figma of 2odB to 40dB.

Gd y slmking, tlwo kadscts us heavier and Less mmfortablo to wcu.

Ingsnml,tbsoomfortofberdsetsdepmdsuprm

their weight, padding and dssign.

In the head& cpnaeetinO able, ptsvent coupling be-weu~the microphone and headphone leads by using at I& a

shielded wire for the micmphone, aad a seporrte pair of wires for the hcdpkm@). &ttor isolation may be possible with a twisted, shielded pir for the micmpbne leads. Do not allow hadphone ground to mutact

micmphw ground or shield. Tie the shield to microphone

PracticalLoudllw TheuserSt.tionuuproduce.aSPLof ground or miuopboae low. Do not tie the shield to the 111 dB in each or of a DT109 or DTlO8 headset. LMV case of the Mnncetor or the case of the user station. In impdance htPdstts such as the DTlO8 and DT109 gcaeral themaximum lmgth for the headset cable is ten feet

heodsets,uusstheuserstationto~morrpaw~from(3.1 meters). Lar@ over ten feet require a special the power supply. With DT109 hdsets, CM300mM300 exteasion able. Check with RTS Systems for help with peak cumnt is 75 milli.mpWe. The CM300URM300L longer cables.

mak currsnt is ismillhoeres. With 600 ohm bdpbcmes, peak eumnt d 30milli.mpnss for the CM3001RM300 user sation. 40 m i l l i ~ ~forb the CM~OOURM~WLuser mion. (quissc2at c u m t is

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and tbs

mi= p d .