We have just had our phones changed at work and now it seems I can no longer toggle between my base phone and my Plantronics CS55 wireless headset? The new phone is a Cisco IP Phone 7945. I have tried plugging the headset into the marked headset socket and the phone handpiece into it's marked socket -- this allows me to only use the phone handpiece - no matter what else I try. I physically have to plug the headset into the handpiece socket - then I can use the headset but no longer can I use the handpiece??

SOURCE: unable to connect jabra t5330 to a cisco ip phone 7941G headset jack

You can solve this by connecting your phone inline.
On the back of the phone where the phone handset plugs into, plug one end of the jabra headset wire & connect other end to the 2nd position (marked by phone & handset). Now plug the handset wire from Ip phone to the 1st position (marked by handset) in the jabra headset. Now you are good to go.

When the phone rings lift the phone handset and answer it with your jabra headset. You can't use jabra with 7941 without lifting the handset on phone.

SOURCE: I have plantronic headset model CS55 the green light is blinking

Either the battery is low, or the unit is switched on.  If you're looking at the base unit of the CS55, on the right hand side there is a switch that either points to I or II.  If it's on II, your headset will be activated the second it is removed from the base.  If it's on I, it won't turn on, thus it won't turn the light on.  Check to make sure that dial is on I instead of II, and when you pick it up you shouldn't have that problem anymore.
If it's a problem with low battery you have to make sure that when you place the headset on the charging cradle that it's securely seated in there.  Also make sure that you clean the charging contacts (the brass-coloured contacts on the headset and on the base) about once a month with rubbing alcohol.

SOURCE: phone doesn't ring in earpiece

Only if you have an HL-10 lifter installed... you will then be able to hear three short beeps in your ear to indicate the phone is ringing.

SOURCE: plantronics CS55. When using the wireless headset

Echo is usually caused by the transmit (speak) level on the unit being set too high.

1. First, try lowering the volume of the telephone. If you still hear an echo, adjust the volume of the headset itself.

2. The master transmit controls of the headset are the ABCD switch settings on the bottom of the base. A is the lowest and D is the highest setting.

3. You can fine tune this setting with the plus (+) and minus (-) buttons on the back of the charging base.

4. If this doesn't fix the echo, try moving the configuration dial on the left side of the charging base. The recommended setting for most phones is 1.

SOURCE: outside caller hears themselves in an echo

Echo is usually caused by the transmit (speak) level on the unit being set too high.

1. First, try lowering the volume of the telephone. If you still hear an echo, adjust the volume of the headset itself.

2. The master transmit controls of the headset are the ABCD switch settings on the bottom of the base. A is the lowest and D is the highest setting.

3. You can fine tune this setting with the plus (+) and minus (-) buttons on the back of the charging base.

4. If this doesn't fix the echo, try moving the configuration dial on the left side of the charging base. The recommended setting for most phones is 1.