The Switchboard SB-22() is a small
portable field type telephone switchboard equipped with 12
individual plug in line units. Connection between lines and
made with plugs and cords. The cords are of the retractable
type. Included with each A version switchboard is an
MX-2915()/PT, Accessory Kit (or an MX-230 Accessory Kit for the
SB-22) containing sub assemblies to increase the line capacity
when the switchboard is operated in tandem with another SB-22()/PT
switchboard. A sub assembly to provide a common battery
trunk, replacing one line unit is provided. One
Headset-Microphone, is provided with each SB-22()/PT wither
an H-81A/U or H-144()/U and/or maybe the H-182()/PT
As far as I can tell the only difference between the -22 and
-22A is that the Accessory Kit for the -22A has one TA-326 Trunk
Pack and 2 TA-222 standard link packs. The Accessory Kit
for the -22, the MX-230, has 3 each TA-222 Standard Line
packs. The SB-22A Housing is plastic whereas the SB-22
housing is aluminum.
The SB-22B is like the SB-22A except the operator pack is
replaced with one that has the DTMF (Wiki) dialing pad
built in.
The SB-22 is what's called a Local Battery (LB) type of board,
meaning that the phones used to ring the board need to have hand
generators.
The call indicator on the SB-22 does not respond to Common
Battery (CB) or Common battery Signaling (CBS) operation modes.
Although the Army calls this a switchboard it's more properly
called a cordboard. This is because switches are not used
to interconnect the lines, pull out cords are used.
Switchboards do not use cords and instead the lines are
interconnected by operating switches.
May have started service in 1952 and still current in a number
of organizations.
Dual Capacity Switchboard
A single SB-22() will have 12 Line packs and 1 operator
pack. A second SB-22() can be configured as an expander by
removing the operator pack and adding 5 Line Packs, taken from two
Accessory Kits, one accessory kit per SB-22(). Now the
unmodified, bottom SB-22() has 12 Line packs and the top SB-22()
has 17 Line packs for a total line count of 29.
Note that the latch that holds the lid on the SB-22() for
transport, can also hold the lid above the SB-22() to act as a
place for reminders. When two SB-22() are stacked this
same latch mechanism will allow the two to be solidly connected
and then have one cover attached to the top. The manuals
don't mention it, but the cover could also be attached pointing
down to angle the face of the switchboard up to face the
operator.
In one configuration the SB-22() will have one or two TA-326
Common Battery "Trunk" Line Packs installed and these are routed
to the line packs on a SB-86/PT which is a 30 or 60 line
switchboard where each line can be either a LB/magneto phone or
a CB signaling phone, or in this case a CB interface to the
SB-22(). The SB-86 may have one or two lines connected to
the POTS.
The -12 manual does not mention it, but to get the Audio or
Visual call alarms to work for the second SB-22 the ground and
NA binding posts on the back need to be connected. If this
is not done there will be no notification of a call ringing the
operator other than the visual indicator on each line pack.
SB-22/PT NSN 5805-00-257-3602
SB-22A/PT NSN 5805-00-715-6171
Component Parts
TA-222()/PT Line Pack
12 are installed in a stock SB-22(). These are
for field phones operating n the Local Battery mode with
generator signaling to the operator.
The main components of this line card are:
- Reel holding the PJ051R plug
- Jack for operator's plug to hear where the calling party
wants to be connected
- Diode
- Mechanical Indicator turns white when ring is detected
and stays white until the operator's plug is
inserted. It has two wires in addition to the ground
connection and is mechanically reset from the operator's
jack which is adjacent on the front panel.
- Lightning Arrestor across the line
TA-326/()/PT CB Trunk Pack
This is an optional Line pack in the MX-2915
Accessory Kit and can be used to replace one of the standard
TA-222 Line packs to give the SB-22() the ability to connect
to the CB switchboard.
The main components of the TA-236 are the same as the
TA-222 plus:
- a 0.5 Henry inductor
- 2 capacitors
- a switch that's activated when the PJ051R plug is
withdrawn from the Line Pack
- the operator's jack has one less contact set than on the
TA-222
Can this connect to the POTS? See below.
1 each TA-221()/PT Operators Circuit
My operator's pack is not working. The 1/2"
diameter by 1" long black capacitor has developed a case of
brown hair growth. Probably needs to be replaced.
Need schematic to troubleshoot.
Production Figures for the TA-221()/PT
Prior to 1985: a whole bunch
July 1985 17,618
units @ $33.46 each
July 1997 1225
units procured.
July 2000 750
units @ 69.80 each
Apr 2001 600 units
@ $60.00 each
Dec 2001 1240 units
@ 58.89 each
Dec 2002 1000 units
procured
data from Mike (21 March 2008)
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This
is the version where you MUST plug into the pack to
disconnect the battery.
Mike found this for me on eBay, New Old Stock
cardboard carton marked:
5805-00-503-3341
p/n SC-DL-84551 (TA-221/PT)
1 ea.
SP056-00-W-0114
M41-?/00
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This
shows the buss on the back side.
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1 each H-81A/U, H-144/U, H-144A/U or
maybe H-182/U Headset-microphone
The connector on the operator's pack is a standard military U-77 type and so any
handset, like the H-33()/PT, or headset that has this
connector should work.
Although it's supposed to be possible to store the operator's
headset in the SB-22 lid, there must be some trick to get it
to fit.
Here is how to fit the headset courtesy of D.S. Karlsen:
1 each MX-2915()/PT Accessory Kit for
the SB-22A
The
MX-2915 box is designed to hold 5 Line Packs, but only 3 come
with it,
2
TA-222 Local Battery Line packs and 1 TA-326 Trunk Line Pack
or
1 each MX-230/PT Accessory Kit for the SB-22
This is probably the only difference between the -22 and
-22A.
MX-230A Accessory Kit
Very similar to the MX-2915
Description SB-22D
This showed up on eBauy from Lithuania early in 2016.
The main difference is the inclusion of a dial in the lid
(hopfully) allowing POTS dialing.
The back has two additions, (1) a multipin Jones type socket
(maybe for connecting to another switchboard) and (2) a U-77
terminated cable (maybe for connecting to the dial).
Intended Use
Switchboard Telephone Manual SB-22()/PT is used for:
- inter-connecting local battery telephone lines,
- local battery telephone lines to local battery trunks,
- local battery telephone lines to common battery trunks and
- interconnecting voice frequency telegraph lines or lines
equipped for remote control radio communication.
- interconnecting with the SB-3614 digital switchboard
Use with POTS
Can the TA-326 "CB Trunk Pack be connected to the POTS to allow
any of the phones on the SB-22() to interconnect to the
POTS? See Connecting to POTS
below.
Answer: Yes, but only under the control of an
operator. The TA-326 goes off
hook as soon as the cord is pulled from it or as soon as a plug
is placed in it's jack. So you can not make a connection
between the TA-326 and one of the line packs and leave the
connection.
You might be able to make a connection with the POTS through a
normal line pack permently to one or more line packs that have
phones that work in CB or CBS modes and have dialing capability,
such as a TA-312 with TA-955 or a TA-838.
Operation
DC Power
There is a long battery holder in the back that holds 4 each
"D" cells. Two of these (3 Volts) are connected by wires
to terminal pair 14 to provide the talk battery for the
operator's headset and is required for operation of the
board. The other two "D" cells are connected with wires
to terminal pair 13 and provide the power for the Night Alarm
buzzer and/or light. The board can be used without the
night alarm. The Terminals in back are:
Pair
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Function
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1 - 12
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Line Packs
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13
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Night Alarm 3 V.
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14
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Oper. Talk Batt 3 V
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15
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Emg Oper phone
TA-977 Touch Tone Dial
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16
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Ring Generator
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17
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Start Power
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Saving the Talk Batteries
Some Operator's packs have a jack and when the
operator's plug is placed in this jack it opens the DC path
from the talk batteries to the operator's headset
mike. If the headset, or handset, is left connected to
the board without placing the operator's plug into the jack
the batteries will be drained.
My SB-22 operator's pack does not have this jack, so the
headset, or the H-33 handset needs to be disconnected when
not in use.
Connecting the SB-22 to the POTS
When a TA-326/()/PT CB Trunk Pack is installed and
connected to the POTS the board is on hook until:
- The cord is pulled out of the TA-326. Just pulling
out the cord takes the switchboard off hook.
- If the cord from any of the normal TA-222 Line Packs, or
the operator's pack is plugged into the Trunk Pack the
board goes off hook.
- An incoming call (ring) will drop the call indicator and
the operator can then anwswer the call. If the
operator is not present you can not use the TA-326 to
connect one of the phones to the outside line because any
connection to the TA-326 takes the outside line off
hook. You can use the standard TA-222 line pack to
connect a phone that's compatible with the POTS such as
the EE-8, TA-1,
TA-46, TA-838, TA-341, etc. which can be used to
answer incoming calls. In order to dial out a TA-312 with the TA-955 Touch Tone
adapter, TA-341,
TA-838 could
be connected to the TA-222 line pack. More than one
phone can be connected to the outside line by daisy
chaining line packs.
If a TA-312, with the TA-955 Touch Tone adapter installed, is
connected to one of the normal trunk packs there is no way to
signal the SB-22, since it does not support CB or CBS
signaling. I.e. the ring generator crank is covered by a
metal plate specifically there to prevent it's use as part of
the TA-955.
Connecting a TA-312 to
the TA-326 CB Trunk Pack
This does not work. Although the TA-312 will work
on the POTS as a CB phone (and also probably as a CBS phone)
the TA-326 does not detect when the TA-312 goes off
hook. So the TA-326 is intended for use in connecting
the SB-22 to either the POTS or to a higher level
switchboard that supports CB signaling.
Video TA-977 Touch Tone Pad & TA-326 Trunk Pack
Calling Time
YouTube
- 31 seconds 1.3 MB
Video Placing a Call
YouTube
- 42 seconds 2.1 MB
Notice that the call indicator drops before the buzzer is
turned on for the demo.
At the end of the call the TA-312 rings off, so after
unplugging the connection you should use the same cord to
clear the call indicator.
"Little tip about the ring off. The reason the one indicator didn't change until you plugged a cord into it was a cord being plugged in is required to reset. The procedure for ring off at the switchboard is to plug the operator jack into the calling station's jack and listen to see if the line is idle or if they are requesting assistance (such as a conference call), this resets the drop. If the line is idle, THEN, the cord is unplugged from the called station's jack."
John
McFerren
After years of storage, with the "D" cells removed, the board
did not work. It turns out that the "D" cell holder is
very similar to two flashlights made as one unit back to
back. The center part is all metal and has two springs for
the battery negative terminals. Two aluminum tubes thread
into the center section and into end caps. All of these
threaded joints carry the negative battery current. They
had developed some rust raising the resistance of the negative
path on one of them to about 27 Ohms, enough to prevent the talk
battery or buzzer from working, depending on which way the
battery holder was placed into the clips.
After cleaning both inside and outside threads I applied Contax
made by Blackburn. Mine is in the 4 oz bottle model
CTB. This black goo was made for making electrical joints
between Aluminum and copper wires. It is called an oxide
inhibiting compound.
I also replaced the operator's pack cord with a new one from a
new line pack in the MX-2915. These have a spring inside
the strain relief boot that looks like it will last longer than
the stock cord that had the rubber strain relief boot split into
two parts.
Replaced one of the standard line packs with a Trunk Pack in the
position next to the operator's pack.
Some Operator's Pack tips from Dag Karlsen in Norway: http://www.classicrotaryphones.com/forum/index.php?topic=20588.msg237423#msg237423
