Frequently Asked Questions

1. How far apart can you put stations?

Answer: For two handsets or headset-chestsets you can put them up to 30 miles apart if you use at least 18 AWG twisted-pair wire. For multiple sets consult the table below. As long as you use 18 AWG twisted-pair wiring, the main concern is the number of sets on the line, not the length of the cable run. Output below 70 dB is considered less than optimum for good communications performance.

H-200/U Headset-Chestsets in receive mode
Line
length
 Line
resistance
(ohms)*
1 set
2 sets
3 sets
4 sets
5 sets
6 sets
dB
Ref.
Loss
Loss
Loss
Loss
Loss
50 feet
0.7
91
0.0
0.0
0.0
0.6
0.9
1000 feet
13
91
0.2
0.4
0.5
1.2
1.7
2000 feet
26
91
0.3
0.5
1.0
1.6
2.1
1 mile
69
90
0.7
1.3
2.0
3.0
3.7
5 miles
344
88
2.3
4.1
5.7
7.2
8.5
10 miles
687
86
3.3
5.7
7.8
9.5
10.7
20 miles
1375
83
4.2
7.0
9.2
10.9
12.3
30 miles
2062
80
4.6
7.6
9.8
11.7
13.1
* 18 AWG: 6.51 ohms / 1000 feet
2. Which products are Bureau of Mines / explosion proof approved?

Answer:

• Call-Signal Stations:

3. Don’t I need some kind of power source or battery to operate the system?

Answer: Sound powered equipment never requires external power source – except the AM-2210N/WTC Sound Powered Telephone Amplifier. Never apply power of any kind (battery or external AC) to the sound powered telephone talking network!

4. Which products are UL approved?

Answer: 702019-003 - Handset; 4.5 foot cord; PTO switch

5. Do I really need to use twisted-pair wiring?

Answer: Yes - because electrical noise on lines can interfere with the low-level sound powered audio signals. That’s not say that you can’t get reasonable performance without using twisted-pair wiring, but for best performance we strongly recommend using twisted-pair.

6. How do you signal a remote location using sound powered equipment?

Answer: This requires a hand-cranked generator at the calling location and a howler at the remote station. All Call-Signal Stations contain a generator to signal a called station and a howler to receive incoming call signals. The generator signal from the calling station can also be used to drive an extension howler at the remote station or to operate a remote relay that can turn on a lamp as a signal.

7. What’s the difference between “press-to-operate” and “press-to-talk”?

Answer: Some handsets and headsets contain switches to operate.

8. Environmental conditions - operating temperatures?

Answer: All military (MIL-T-15514) products meet a storage temperature range between -40 degree c and +77 degree C. Bear in mind, that at least for handsets and headsets, a human being has to be present for operation!

The AM-2210N/WTC Sound Powered Telephone Amplifier has an operating temperature range from -40 to +149 degrees F at 95% RH.