🚀 go-pugleaf

Although I am getting tired of seeing requests for information about
line in-use indicators and speakerphones, I wanted to say a few things
since everyone has to make decisions about station equipment now.

About line in-use lamps:
I have a phone line connected to 5 stations.  I have installed an "S"
relay from an *ancient* KTU in series with one conductor of the line as
it enters the premises.  The "S" relay is designed to be connected in
series with the line and sense an off-hook condition.  It has a set of
normally open contacts which I have wired in series with a
Princess-style lighted dial transformer and Type 51A lamps in Type 15
lamp sockets.  The lamps are wired in parallel and are located beside
each station.  I have used all telco-spec parts, but a 6V transformer
and regular 6V bulbs in regular sockets could be used.  A different
relay could also be used.  I recommend the Rubbish Shack 6V ~500ohm coil
impedance model in the clear plastic case.  Also, the contacts on the
relay can be used for other things such as exclusion on modem lines (to
disconnect the regular phones from the line when the modem is off-hook)
or for the automatic control of a tape recorder on the line (it is
activated by an off-hook condition.  I used the Yel/Blk pair in the quad
to light the lamps.  This is a great no-maintenence system for those who
are not too squeamish about working on their inside wiring, since it
cannot simply be plugged into an RJ-11 and must be connected in series
with the line before first station.
I saw another circuit that is basically like DAK's "Drew's Brainstorm"
which can be plugged into an RJ-11.  It was published in
Radio-Electronics in '80 or '81.  It looked like a good circuit.

About speakerphones:
I have a normal full-duplex speakerphone which I use occasionally, but I
use two other speakerphones which I use more often.
The first is not really a speakerphone; instead, it is a Western
Electric 30D Voice Coupler designed for primitive phone patch applications.
It is used to provide a protected audio path between the phone line and
random audio equipment (two-way radio, broadcast radio/TV, etc.).  It
consists of bridging capacitors, matching xfmrs, a low-pass pi network,
and a fused connection to the audio equipment.  With this, I have
connected my stereo to the line in a way that does not present a DC load
to the line (so it does not affect the on-hook/off-hook status of the
line).  Whenever I am put on hold, I simply flip a switch on the stereo
and put down the phone handset.  I will post a schmatic of a simplified
voice coupler if there is demand.
The other speakerphone is very handy, although it is not commercially
available and would have to be homebrewed.  It is connected to a
photocell pointed at the ceiling lights in the room.  If the lights are
on (when the room is occupied) and the phone rings, the circuit
automatically answers on the first ring and connects the full-duplex
speakerphone.  The occupant then says/shouts (depending on room size/mic
sensitivity) "hello!" and usually picks up a regular phone and continues
the conversation.

If you want schmatics for any of the above or anything similar, send me
mail and I'll see what I can do.

I am very disturbed about one message I read.  The person proposed to
use modular telephone connectors for connecting RS-232 serial lines.
I think this is a BAD IDEA.  Modular plugs were developed to connect
telephones and only telephones, and that is how they should be used lest
some bozo should happen to plug an RS-232 cable into a telephone jack
and fry the serial card with -48V when it wants +/-12V or, worse yet,
cause damage to our wonderful Public Switched Telephone Network.

-Ross (rdsnyder%ccc@eddie.mit.edu)