Information Technology Reference
In-Depth Information
jacks.in.our.homes.and.businesses.out.to.telephone.poles,.or.
perhaps.buried.cable.runs,.join.up.with.large.bundles.of.other.
copper.cables,.and.eventually.end.up.at.the.phone.company's.
switching.station,.or.possibly.connect.to.a.box.that.connects.
them.to.a.digital.concentrator.
But. let's. start. at. the. beginning.. The. telephone. is. a. very.
simple. device. that. contains. very. few. parts,. no. matter. how.
modern.it.is..Basically,.there.is.a.microphone.that.picks.up.
your. voice. and. translates. those. sound. waves. into. different.
modulated.currents.of.electricity.that.are.transmitted.over.the.
copper.wires..There.is.a.simple.switch.of.some.sort.that.con-
nects.you.to.or.disconnects.you.from.the.telephone.system..
Then. there. is. a. speaker,. which. translates. those. modulated.
currents.of.electricity.into.sound.waves.that.you.recognize.as.
the.speech.of.your.grandma.in.Miami.Beach.
There.also.is.some.type.of.mechanism.for.telling.the.sys-
tem.who.you.want.to.talk.to..The.POTS.systems.used.“pulse.
dialing.”.The.dial.on.the.phone.would.basically.click.the.con-
nection.switch.as.many.times.as.you.indicated.by.the.distance.
you.turned.the.dial..So.if.you.stuck.your.inger.into.the.nine.
hole.and.turned.the.dial.to.the.little.metal.block.that.stopped.
your.inger.(see.picture.of.original.black.dial.phone),.then.let.
go,.as.the.dial.returned.to.its.starting.position,.it.would.click.
that. switch. nine. times,. pulsing. that. signal. nine. times,. and.
letting.the.system.know.that.you.just.sent.the.number.nine.
(Figure 3.9).
Somewhat.newer.phones.replaced.the.dial.with.a.keypad.
that. generated. different. frequencies. down. the. line. that. cor-
responded.to.the.number.you.wanted.to.connect.to..And.of.
course,.most.of.us.now.have.telephones.with.computers.in.
them.. Those. computers. store. phone. numbers,. record. mes-
sages,.keep.track.of.different.rings.for.different.callers.or.dif-
ferent.people.in.our.house,.keep.a.contact.list.that.we.can.
look.up,.block.unwanted.calls,.and.much.more.
Many.modern.phones.therefore.require.an.outside.source.
of.power..And.many.of.them,.especially.those.that.are.actu-
ally.radios.and.allow.you.to.use.them.remotely.by.connecting.
