SB-22 Switchboard
© Brooke Clarke, N6GCE |
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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 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.
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
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.
- Lightening Arrestor across the line
TA-326/()/PT CB Trunk Pack
This is an optional Line pack in the MX-2915 Accessory Kit and can beused 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:
Can this connect to the POTS?
- 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
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 eachJuly 1997 1225 units procured.July 2000 750 units @ 69.80 eachApr 2001 600 units @ $60.00 eachDec 2001 1240 units @ 58.89 eachDec 2002 1000 units procured
data from Mike (21 March 2008)
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
This shows the buss on the back side.
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
or1 each MX-230/PT Accessory Kit for the SB-22This is probably the only difference between the -22 and -22A.
Manual
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?
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-325 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.
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
Function
1 - 12
Line Packs
13
Night Alarm 3 V.
14
Oper. Talk Batt 3 V
15
Emg Oper phone
TA-977 Touch Tone Dial
16
Ring Generator
17
Start Power
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: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.
- 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.
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
SB22_Time.avi - 31 seconds 1.3 MB
Video Placing a Call
SB22_call.avi - 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.
Probably all military phones that support magneto signalling will work. This includes the EE-8, TA-312, TA-838 and TA-1.
This is a 16 key touch tone pad that looks exactly like the pad on the TA-955 except it is mounted in a metal box that attaches to the side of the SB-22 (see photo above). Both the keypad and it's cover are hinged so that the keypad can be covered when the box is closed or the keypad is held ready to use when the box is opened.
I got two TA-977s from Steve Hanney because they were both defective. One had a nice box but the wires coming out the back of the keypad were cut off right at the potting. The other box with a nice keypad had a rusted 9 Volt battery box. So I swapped the good keypad onto the good box. Red wire to + 9 Volt battery, Black wire to - 9 Volt battery, White and Green wire to output terminals.Marked: Star Dynamic Corp. Contract no. DAAK80-80-C-0555 - TA-977/PT -
There is no strain relief where the wires enter the potting so as the keypad is opened and closed the wires flex right at the surface of the potting. I used a hot melt glue gun and put a big blob of glue on the wire cover about 1/2" away from where it enters the potting and another glob down in the inside corner of the box. This should cause the wire flexing to be inside the outer cover and not at the potting joint.
There are two terminals, similar to the terminals on the back of the SB-22, push and insert wire into the end, except the body of the terminal is plastic.
Uses a standard 9 Volt battery.
TM11-5805-262-20P and -34P are on line at ETM but TM11-5805-262-12 and -34P is restricted access?MIL-S-10399 is the Military specification that describes the SB-22( ).
TM 11-5805-262-34P Parts list
TM 11-5805-262-35 DS, GS and Depot Maintenance Manual. No theory of operation, but it has numerous troubleshooting and test procedures and schematicsTM 11-5805-262-12 Change 9 mentions an Adapter, Tone-signalling TA-977/PT (NSN 5805-01-040-9653)
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.
