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:

702019-535
702019-545
702019-555
702019-835

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.

Press-to-operate – this switch connects the handset or headset to the sound powered line so the operator can listen as well as talk on the network.

Press-to-talk – this switch connects the transmitter to the sound powered network.

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.